Brittany L. Frazer. A Thesis

Transcription

1 APPROXIMATING SUBGLOTTAL PRESSURE FROM ORAL PRESSURE: A METHODOLOGICAL STUDY Brittany L. Frazer A Thesis Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of Master of Science August 2014 Committee: Ronald C. Scherer, Advisor John W. Folkins Alexander M. Goberman

2 2014 Brittany Frazer All Rights Reserved

3 iii ABSTRACT Ronald Scherer, Advisor The most frequently used method to estimate subglottal pressure noninvasively is to have a person smoothly utter CVCV strings such that the subglottal pressure remains nearly constant throughout the utterance of the string, as in smoothly saying /p:i:p:i:p:i: /, and an oral pressure transducer is used to estimate the subglottal air pressure during the vowels by measuring the oral pressures during the consonants. The current investigation sought to determine the accuracy of estimates of subglottal pressure for various conditions, namely, whether or not the subjects are trained in the use of a standard utterance, increasing syllable rate, using a voiced /b/ instead of a voiceless /p/ initial syllable, adding a lip or velar leak, or using a two syllable production instead of a single syllable production. 10 subjects (5 males and 5 females) volunteered for this study (results for 3 males and 3 females are reported here). The subglottal pressure was estimated from the oral pressure during lip occlusion, and the syllable rate and lip closed quotient (the duration the lips are closed divided by the syllable duration) were obtained for all subjects. Lip leak, velar leak, and lack of time to equilibrate air pressure throughout the airway caused estimates of subglottal pressure to be inaccurate. A wide range of syllable rates provided relatively accurate results. In addition, the use of the voiced initial consonant /b/ and the two-syllable word /pip / appeared to create acceptable estimates of subglottal pressure from oral pressure. Training improved the consistency of the oral pressure profiles and thus the assurance in estimating the subglottal pressure. Numerous pressure profile shapes during lip occlusion are discussed.

4 iv This thesis is dedicated to all of the teachers I have had, formally or informally, across my lifetime.

5 v ACKNOWLEDGMENTS I would first like to thank my advisor, Dr. Ronald Scherer for all of the help he has given me in the last five years. He has taught me not only about being a researcher but also about being a professional. Thanks also should be extended to my committee members, Dr. Goberman and Dr. Folkins for helping with document edits and giving helpful suggestions relating to my project. I would like to thank Dr. Goberman, Dr. Tim Brackenbury, Mrs. Karen Brackenbury, and Mrs. Donna Colcord for completing the voice assessments for my thesis. I would like to extend further thanks to each of these individuals for giving me advice about my project. Finally, I would like to thank Martin Perrine. He has given me all of the resources I need to complete any endeavor I attempt in life and I am forever indebted to him.

6 vi TABLE OF CONTENTS Page INTRODUCTION... 1 Relevance of Subglottal Pressure... 1 Direct Measurement of Subglottal Pressure... 2 Indirect Methodology for Recording Intraoral Air Pressure.. 2 Indirect Measurement of Subglottal Pressure 3 General Purpose of the Study. 5 Experimental Factors to Consider.. 6 The syllable string.. 6 Syllable rate 9 Lip closed quotient. 10 Loudness, pitch, and articulation 10 Analysis Factors to Consider. 11 Oral pressure signal shape. 11 Location on oral pressure signal used to estimate subglottal pressure.. 12 Equipment calibration and frequency response. 16 Specific Purpose of the Current Study METHODS 18 Subject Selection 18 Equipment.. 19 Standard Production Condition. 21

7 vii Method Used to Estimate Subglottal Pressure from Oral Pressure 21 PART 1: Untrained Production versus Trained Production.. 23 PART 2: Rate and Lip Closed Quotient PART 3: Initial Voicing 27 PART 4: Misarticulations.. 29 PART 5: Velar Leak.. 31 PART 6: One Syllable versus Two Syllables Analysis. 35 RESULTS AND DISCUSSION 36 Construct of a Pressure Signal Pressure Shapes.. 41 PART 1: Untrained Production versus Trained Production.. 46 PART 2: Rate and Lip Closed Quotient 52 PART 3: Initial Voicing. 58 PART 4: Misarticulations.. 62 PART 5: Velar Leak.. 66 PART 6: One Syllable versus Two Syllables 70 Comparison of Estimates of Subglottal Pressure across Experimental Conditions.. 74 Other Conditions to Consider 84 Lip closed time.. 84 Respiratory pumping.. 85 Cheek compliance. 86

8 viii Nasal inhalation. 86 Calibration and response time of pressure transducer Length of oral pressure tube.. 87 Saliva in the tube 89 CONCLUSIONS 91 REFERENCES.. 95 APPENDIX A 102 APPENDIX B 103 APPENDIX C 104 APPENDIX D 107 APPENDIX E 109 APPENDIX F 111

9 ix LIST OF TABLES Table Page 1.1 Literature Review of Difference Between Actual and Estimated Subglottal Pressure Experimental Tasks Demographics of Subjects Shapes of Lip Occlusion on Oral Pressure Signals with Possible Anatomical Causes of Changes Shape Characteristics of Three Untrained and Three Trained Syllables for Six Subjects Standard Production Condition Training Information Shape Characteristics of Three Faster and Six Standard Production Syllables for Six Subjects Shape Characteristics of Three Voiced Initial Consonants and Six Standard Production Syllables with Unvoiced Initial Consonants for Six Subjects Shape Characteristics of Three Initial Consonants with a Lip Leak and Six Standard Production Syllables for Five Subjects Shape Characteristics of Three Two Syllable Productions /pip / and Six Standard Production Syllables for Five Subjects... 72

10 x LIST OF FIGURES Figure Page 1.1. Vocal Tract Configuration during CVC Oral Pressure Signal for Standard Production Condition Oral and Subglottal Pressure Signals from Smitheran and Hixon (1981) Rectangular Oral and Subglottal Pressure Signals from Hertegård, Gauffin & Lindestand (1995) Non-rectangular Oral and Subglottal Pressure Signals from Hertegård, Gauffin & Lindestand (1995) Various Oral Pressure Signal Shapes Response Time of Pressure Transducer Oral Pressure Signal from Part Oral Pressure Signals Comparing /b/ and /p/ as Rate Increases Oral Pressure Signal Comparing /p/ and / / Oral Pressure Signal Comparing /p/ and /m/ Multi-signals for /p:i:p:/ and /pip / Lip Closure Gesture on Oral Pressure Signal Syllable Rate v. Duration of Pressure Rise During Lip Closing Lip Open Gesture on Oral Pressure Signal Multi-signals for Lip Leak/Misarticulation Condition Vocal Tract Configuration, Oral Pressure, and Oral Flow for Lip Leak/Misarticulation Condition Comparison of Trained and Untrained Oral Pressure Signals Frequency of Oral Pressure Shape Characteristics by Syllable Rate... 56

11 xi 3.8. Oral Airflow and Oral Pressure Signals for Fast Syllables Pressure Change from Standard Production Condition to Lip Leak/Misarticulation Multi-Signal Example of Lip Leak Multi-Signal Example of Velar Leak Estimated Subglottal Pressure Change from Standard Production Condition to Velar Leak Condition Average Oral Airflow and Oral Pressure Signals for Standard Production Condition and Velar Leak Condition Box and Whisker Plot for all Condition for Subject M Box and Whisker Plot for all Condition for Subject F Box and Whisker Plot for all Condition for Subject M Box and Whisker Plot for all Condition for Subject F Box and Whisker Plot for all Condition for Subject M Box and Whisker Plot for Three Condition for Subject F Multi-Signal Example of Reduced Lip Closure Duration as Estimated from the Oral Pressure Signal Oral Pressure Signals Comparing Differences in Oral Pressure Signals when Varying Oral Pressure Tube Length Multi-Signal Example of Untrained Syllable with Highlighted Issues.. 90

12 1 INTRODUCTION Relevance of Subglottal Pressure Subglottal pressure, or tracheal pressure, is an important parameter in phonation. Specifically, when the vocal folds are close enough to each other, a sufficient amount of air pressure must be built up beneath them to initiate phonation (Borden & Harris, 1984). An increase in the average subglottal pressure during speech tends to result in greater loudness (e.g., Gauffin & Sundberg, 1989; Hixon, Weismer, & Hoit, 2008; Kent, 1997; Raphael, Borden, & Harris, 2003), more energy in higher frequencies resulting in a brighter voice (Gauffin & Sundberg, 1989), and a higher pitch (e.g., Board, 1973; Raphael et al., 2003). Subglottal pressure is an important objective clinical variable related to vocal fold tissue health and phonatory function. Depending on the type of pathology presented or the vocal technique being used, the voice patient may have subglottal pressure values that are too high or too low. For example, patients with nodules, polyps, laryngeal cancer, or hyperadduction tend to have an increased average subglottal pressure (Hillman et al., 1989; Kitajima & Fujita, 1992), while patients with contact ulcers may have normal values of subglottal pressure (Hillman et al., 1989), but patients with voice production that is too soft may have low subglottal pressure values (Holmberg, Hillman, & Perkell, 1988). The variation of subglottal pressure depending upon vocal fold tissue conditions and vocal technique strongly suggests that subglottal pressure should be a standard measure in the voice clinic (Fisher & Swank, 1997). Refined clinical measures derived from subglottal pressure, including phonation threshold pressure and collision threshold pressure, depend on the accuracy of subglottal pressure estimates (Enflo & Sundberg, 2009; Fisher & Swank, 1997). This means that the measurement of subglottal pressure needs to be made accurately both for clinical and

13 2 research purposes. It then can be used to objectively describe the effects of vocal fold tissue damage or deviant vocal technique, and help document improvement in vocal health and function following treatment. Direct Measurement of Subglottal Pressure Subglottal pressure has been recorded both directly and indirectly. Direct measurements are typically obtained with a percutaneous needle puncture of the cricothyroid membrane into the trachea (e.g., Gramming, Sundberg, Ternström, Leanderson, & Perkins, 1988). A pressure transducer connected to tubing inserted into the trachea, or placed directly within the trachea, collects the dynamic pressure within the trachea (e.g., Sundberg et al., 2010). The direct method is invasive, and thus indirect methods have been adopted. The research discussed in this thesis is a methodological study of a particular indirect and often-used method whereby intraoral air pressure is used as an estimate of the subglottal pressure. Indirect Methodology for Recording Intraoral Air Pressure Typically an aerodynamic system is used that measures both the intraoral air pressure (Hixon, Weismer, & Hoit, 2008) and the airflow (to determine unwanted air leaks; Fisher & Swank, 1997; Solomon & Helou, 2013). The pressure transducer for measuring the intraoral pressure is connected to a short tube that is placed between the lips allowing for an air-tight seal when the lips are closed, and the airflow is obtained with the aid of a flow mask (e.g., Glottal Enterprises aerodynamic flow mask system, MSIF-2 S/N 2049S).

14 3 Indirect Measurement of Subglottal Pressure The goal of measuring subglottal pressure is to know the pressure below the vocal folds during the production of a vowel and voiced or voiceless consonants. Measuring oral air pressure during lip occlusion of the consonant while producing CVCV (C= consonant, V= vowel) strings, where C is a bilabial consonant, is a technique used to estimate the subglottal pressure (Löfqvist, Carlborg, & Kitzing, 1982; Rothenberg, 1973; Smitheran & Hixon, 1981). The air pressure is measured in the oral cavity during the consonant lip closure just before and just after the adjacent vowel, not during the vowel, and is used to estimate the subglottal pressure during the vowel. The syllable string, when performed in a certain manner (to be discussed), provides the same pressure in the oral cavity during the consonant production as in the trachea during the vowel (see Figure 1.1) when there is sufficient lip closure duration to equilibrate the pressure throughout the airway. The method of using oral air pressure to estimate subglottal pressure is supported by the understanding that air pressure in a system becomes equilibrated when the source pressure remains the same after a downstream location of the system is occluded. When the downstream end is fully occluded, flow stops and pressure becomes constant throughout the system; source pressure (here, lung pressure) is equal to the pressure downstream (here, oral pressure) (Figure 1.1). This occurs during the lip occlusion when there is sufficient vocal fold abduction to allow air to move into the supraglottal vocal tract without vocal fold vibration and equalize the air pressure throughout the entire airway before the /p/ plosive release (Mehta & Hillman, 2008). Using the stop consonant /p/ plus a following sustained vowel (V) as the syllable, repeated to form a /pv:/ syllable string (i.e., /pv:pv:pv:pv:pv:/ ) and produced in a very smooth manner (that is, with no abrupt changes in airway volume during the lip occlusion), tracheal pressure

15 4 during the vowel and equilibrated oral pressure during the stop plosive are assumed to be equal, just before the stop release (Smitheran & Hixon, 1981). Figure 1.1. Vocal Tract Configuration during CVC. The figure shows the configuration of the vocal tract during the production of a /CVC/ string. The glottis is open during the consonant production, but the lips and velopharyngeal port are closed resulting in a buildup of oral air pressure behind the lips in the oral cavity (shown as the arrow). During the vowel production, the mostly closed position of the vocal folds causes the air pressure to build up below them (again, shown as the arrow). If the only change made to the phonation system between the production of the consonant to the production of the vowel back to the production of the consonant is the opening/closing of the vocal folds and lips, then the air pressure built up behind the lips during the consonant production and the air pressure built up beneath the vocal folds during the production of the vowel are equal, and thus the pressure is the same at all three locations marked by the arrow. The task requires that the same respiratory effort be used throughout the string to guarantee no change in lung pressure. The accuracy of this indirect method of estimating subglottal pressure has been studied. Löfqvist, Carlborg, and Kitzing (1982), McHenry et al. (1995), Kitajima and Fujita (1990), and Hertegård, Gauffin, and Lindestad (1995) have compared simultaneous direct subglottal pressure measurements and intraoral pressure measurements and found little difference between them (see Table 1.1).

16 5 Table 1.1 Literature Review of Difference Between Actual and Estimated Subglottal Pressure Löfqvist, Carlborg, and Kitzing (1982) McHenry et al. (1995) Kitajima and Fujita (1990) Hertegård, Gauffin, Lindestad (1995) mean difference: cm H2O; SD: cm H2O mean relative error across three loudness levels: 13.39%; SD: 9.04% mean difference of normal subjects: 0.9 cm H2O; SD: 0.5 cm H2O less than 5% difference The difference between estimated subglottal pressure (the equilibrated oral pressure) and measured subglottal pressure for each of the four studies that compare the two measures. Note: Kitajima and Fujita s (1990) study included subjects who have had a laryngectomy. This table only includes data from the normal subjects. (SD: standard deviation) General Purpose of the Study The accuracy of the estimate of subglottal pressure via intraoral air pressure measurements depends on proper recording methodology and analysis of the intraoral pressure. This study examines the methodology of estimating subglottal pressure via intraoral pressure. The goal is to determine how inaccuracies in pressure measurement might result and thus can be avoided in clinical and research settings. The study adopts a standard technique that is presumed to give highly accurate subglottal pressure estimates, and then determines what pressure changes are created when that standard is not complied with, indicating possible measurement errors in practical settings. The study has been motivated by the observation that the occlusion pressure patterns reported in the literature have varied a great deal, suggesting that some of those varying patterns may not provide accurate subglottal pressure estimates for the adjacent vowels. For example, a pressure pattern that is highly pointed rather than flat during the production of the stop consonant /p/ in the /pv:/ sequence suggests that there has not been enough lip closure time to equilibrate the pressure. The relatively tall pointed shape may also

17 6 suggest that there was abrupt vocal tract volume decrease, transiently increasing vocal tract air pressure. Both conditions produce inaccurate pressure estimates (the first too low, the second too high). The genesis for these and other kinds of patterns will be explored in this study. The pressure signal in CVCV sequences using the standard technique is shown in Figure 1.2. The syllable rate, or how fast the syllable is repeated, is approximately 1.5 syllables per second. This rate has been noted by some as the ideal syllable rate (Smitheran & Hixon, 1981). The duration for the consonant and the vowel segments is nearly equal. This represents the near 50% lip closed quotient, or a lip closure time (vocal tract occlusion duration) that is equal to half the duration of the CV syllable. Figure 1.2. Oral Pressure Signal for Standard Production Condition. This figure shows the oral pressure signal for a CVCV sequence, namely /p:i:p:i:p:i:p:i:p:i:p:i:/ at approximately the standard production condition (here the syllable rate is 1.3 syllables per second and the lip closed quotient of 44%). The raised portion of the pressure signal corresponds to the length of time the lips are closed during the consonant (x-axis) and the amount of pressure that builds up behind the lips (y-axis, here an arbitrarily assigned value). The flat baseline portion corresponds to the time the lips are separated during the production of the vowel (x-axis) during vocal fold vibration (the baseline is shown with its minor acoustic pressure variations). Here, the shape of the pressure signal is nearly rectangular or plateaued. A flat plateau is considered the ideal shape because it assumes that the air pressure in the mouth (shown as the top relatively flat plateau) during the consonant is equal to the pressure below the vocal folds during the vowel. Experimental Factors to Consider The syllable string. Repetitions of the syllable /pi:/ are generally chosen for the purpose of obtaining estimates of subglottal pressure from the values of the oral pressure during the lip occlusion for

18 7 /p/ (Hertegård, Gauffin, & Lindestad, 1995; Löfqvist, Carlborg, & Kitzing, 1982; Smitheran & Hixon, 1981; Thompson & Hixon, 1978). This has been done for several reasons. Firstly, the validation studies mentioned above typically used that syllable string (i.e., McHenry et al., 1995). Secondly, /pi:/ repetitions are chosen due to the anterior nature of both phonemes: anterior phonemes help to ensure velar closure during the production of the consonant string (Smitheran & Hixon, 1981; Thompson & Hixon, 1978). High vowels such as /i/ tend to offer increased and more consistent velar closure than low vowels (Moll, 1962). However, Rothenberg (2013) indicated that all other vowels apart from diphthongs are also acceptable for inferring subglottal pressure, although he did not provide evidence for this statement. Other validation studies mentioned above have used /pa:/ (Hertegård, Gauffin, & Lindestad, 1995; Löfqvist, Carlborg, & Kitzing, 1982) or /i:pi:/ (Kitajima & Fujita, 1990) as a syllable string. Thirdly, the voiceless stop consonant /p/ is thought to facilitate more accurate estimates of subglottal pressure than voiced stop consonants due to less resistance to airflow through the glottis and thus faster pressure equilibration throughout the airway (Arkebauer, Hixon, & Hardy, 1967; Bernthal & Beukelman, 1978). Rothenberg (1982) suggests, in response to Smitheran and Hixon (1981), that /bvp:/ strings be used in lieu of /pi:/ syllable strings. This articulatory gesture reduces the potential for aspiration (and thus a pressure drop) during the /p/ plosive release while providing adequate abduction during the voiceless /p/ to equilibrate the airway pressure. The aspiration during the /p/ lip occlusion release is the result of a laryngeal opening gesture that inhibits vibration of the vocal folds (Löfqvist, 1995). The accuracy for approximating the subglottal pressure during the /p/ should be high, while not wasting air or causing large lung volume change during an aspiration (e.g., Konnai, 2012). Löfqvist and Gracco (1997) found that there were inconsistent

19 8 yet minimal differences in lip mechanics between voiced and voiceless consonants, noting that the major difference was the laryngeal activity. It has yet to be determined whether a voiced or voiceless stop plosive as the initial consonant of the syllable string (i.e., /bv:p:bv:p:/ versus /p:v:p:v:/ strings) yields the more accurate estimate of subglottal pressure. Rothenberg (2013) further challenges researchers to use more natural speech to estimate subglottal pressure. He proposed words such as pepper, apple, spa, and papa. McHenry et al. (1996) used /pi:/ syllables, as well as the all-voiced sentence A man and a woman were ambling along a one-mile lane near Rainy Island Avenue, and a spontaneous monologue as utterances in their study of laryngeal airway resistance measured by direct and indirect methods. They found that the syllable repetition task produced the least amount of pressure measurement error (13.4% difference between oral pressure and subglottal pressure), followed by the monologue task (23% difference) and the sentence task (33.5% difference). McHenry et al. (1996) measured the percent difference for the monologue task and sentence task from a section of 100 ms of continuous voicing for men and 50 ms of continuous voicing for women. The monologue, having no voiceless stops, runs the risk of never having sufficient time during the voice consonants to equilibrate the pressure throughout the airway. Similarly, if the monologue is without voiceless stop consonants or if stops are too short and are not accompanied by respiratory pumping (abrupt lung volume change) the results of the monologue task may not have equilibrated pressure in the airway. Despite this, these results appear reasonable. However, both Rothenberg (2013) and McHenry et al. (1996) urge researchers to use stimuli that may more accurately reflect how the larynx functions when normal speaking strategies are employed. This might be a useful suggestion, but the manner of speaking must be such that there is identifiable equilibration of the air pressure throughout the airway at meaningful moments of the utterance.

20 9 Syllable rate. The optimal rate of syllable repetition during recording has been debated (Hixon, 1981; Rothenberg, 1981). Knowing if there is an optimal rate (or optimal range of rates) is important because an optimum rate can help to ensure full lip and velar closure, which is necessary to obtain accurate estimates of subglottal pressure from oral pressure. That is, lack of lip or velar closure may produce a constant flow leak that does not permit the full buildup of the oral pressure to equilibrate the pressure throughout the system during the lip occlusion. A syllable rate of 1.5 syllables per second has long been accepted as the standard (suggested by Smitheran & Hixon (1981), and noted by Netsell, Lotz, DuChane, & Barlow, 1991). Additionally, Smitheran and Hixon (1981) reported that in a pilot study (Thompson & Hixon, 1979) a syllable rate below 1.5 syllables per second had periods of velar opening, altering the estimates of subglottal pressure. Thompson and Hixon (1979) chose three syllables per second for their research because a pilot study revealed that young children could execute this syllable rate reliably. Netsell et al. (1991) estimated subglottal pressure using the syllable rates of 1.5 syllables per second and 3.0 syllables per second. In their healthy adult subjects, there was a minimal increase in estimated subglottal pressure at the higher syllable repetition rate. The subjects in the study by Hertegård, Gauffin, and Lindestad (1995) produced repetitions of the /pa/ syllable at rates of 1.3 syllables per second and 2.3 syllables per second. Although both syllable rates resulted in close estimates of subglottal pressure from oral pressure, the majority of the productions at both syllable rates were categorized as having pressure signals with peaks rather than flat plateaus. A syllable rate of 1.3 syllables per second resulted in a greater percentage of peaked oral pressure signals during the syllable repetition task. Hertegård et al. (1995) also noted that many of the subjects produced the slower syllable rate with a more breathy

21 10 and pressed (labeled hyperfunctional by the authors; p. 150) voice quality. No consensus about the most appropriate syllable rate for estimating subglottal pressure from oral pressure has been found to this point in the literature. Lip closed quotient. It is curious that the duration the vocal tract is occluded at the lips relative to the duration of the CV syllable apparently has not been studied. This appears to be a highly relevant characteristic of the procedure in that it takes time to equilibrate the air pressure throughout the airway after the vocal tract is occluded. Kitajimo and Fujita (1990) reported the lip closed time for their subjects. The times ranged from 160 to 280 ms but were not found to impact the differences found between subglottal pressure and intraoral pressure. This suggests that shorter lip closure times may lead to errors in estimating subglottal pressure from oral pressure. [Closure times and lip closed times must also be longer than the response time of the oral pressure transducer, about 10 ms in this study here (see Figure 2.1 below)]. This topic will be approached in this study by measuring natural variation in the lip closed quotient (LCQ), i.e., the duration of the assumed full lip contact relative to the duration of the syllable while changes in syllable rate are made. This will answer the questions How much time does it take to equilibrate the air pressure? and What combinations of syllable rate and LCQ appear to give accurate subglottal pressure estimates? Loudness, pitch, and articulation. Relative to loudness and lung pressure, McHenry et al. (1995) found that as pressure increased above 25 cm H2O, estimates of subglottal pressure from oral pressure became less

22 11 accurate, with no directional trend across their six subjects. A study by Kitajima and Fujita (1990) suggests that as loudness increases, oral pressure may become less than subglottal pressure. Their study, however, was performed with those with partial laryngectomy and unilateral paralysis. Numerous authors have noted that when estimating subglottal pressure, there should not be variation in stress of the production. This means that all syllables should be recorded in a legato (smooth) fashion, that is, at a consistent pitch with no changes in respiratory force throughout the entire syllable string (e.g., Hertegård et al., 1995). Netsell (1973) explain that air pressure tends to slope in the direction of the stressed vowel, resulting in a pressure signal that has a peak at the beginning if the stressed vowel is before the occlusion or at the end if the stressed vowel is after the occlusion (p. 227). In addition, Hertegård et al. (1995) suggest that the initial consonant should be articulated precisely and consistently to prevent altering the expected estimate of subglottal pressure. Analysis Factors to Consider Oral pressure signal shape. The shape of the oral pressure signal from which the most accurate estimation of subglottal pressure can be obtained has never been firmly established in the literature. Rothenberg (2013) attests to the necessity of flat pressure plateaus to estimate subglottal pressure from intraoral pressure for the surrounding vowels. A plateau, or rectangular shaped oral air pressure signal, suggests that during the flat portion, pressure equilibration has taken place and the airway does not change shape nor the lungs change pressure. Despite the assumption that non-peaked (flat) pressure signals (when there is no flow leak as well) provide the most valid

23 12 measures, there have been many patterns of the oral pressure signal during the /p/ occlusion accepted in the literature. Hertegård, Gauffin, and Lindestad (1995) noted three different patterns of oral pressure signals during the /p/ occlusion: flat, more peaked, and pronounced peaked (p. 151). Flat profiles were suggested as the ideal shape, but slightly peaked signals can also be used to estimate subglottal pressure. The exact causes of shape variations are not well understood, leading to potential errors in pressure estimations due to subject or patient training inadequacy. Researchers have suggested that causes of shape variations can include respiratory pumping (Hertegård, Gauffin & Lindestad, 1995) or punched out syllables (Rothenberg, 2013), stressing vowels (Netsell, 1973), /p/ aspiration (e.g., Hertegård, Gauffin & Lindestad, 1995; Rothenberg, 1982; Rothenberg, 2013), soft phonation (Verdolini-Marston, Titze, & Druker, 1990), velar leak during the stop (e.g., Fisher & Swank, 1997), and choppy phonation (Hertegård, Gauffin & Lindestad, 1995). Location on oral pressure signal used to estimate subglottal pressure. The measurement location on the oral pressure signal must be chosen carefully to determine the pressure estimate. Smitheran and Hixon (1981) estimated the subglottal pressure during the vowel as the average of the midpoints of the oral pressure signal pulses on either side of the vowel (Figure 1.3), while Holmberg (1993) used the average of the peak pressures just before and just after the vowel to estimate subglottal pressure. As previously stated, the peak oral pressure may be the best estimate of tracheal pressure during the vowel due to the equilibrium of the system that occurs at that moment during the stop plosive (Smitheran & Hixon, 1981).

24 13 Figure 1.3. Oral and Subglottal Pressure Signals from Smitheran and Hixon (1981). Example of the location used to estimates subglottal pressure from oral pressure used by Smitheran and Hixon (1981). The location during the vowel is marked by the arrows. Notice the shape of the oral pressure signal is peaked. Adapted from A clinical method for estimating laryngeal airway resistance during vowel production, by J. R. Smitheran and T. J. Hixon, 1981, Journal of Speech and Hearing Disorders, 46(2), p Rothenberg (1973, 2013) suggests that pressure peaks should not be used to estimate subglottal pressure. Hertegård, Gauffin, and Lindestad (1995) estimated the subglottal pressure at the mid-point of the vowel as the amount of oral pressure during the first moment of full lip occlusion of the consonants that surround the vowel (Figure 1.4).

25 14 Figure 1.4. Rectangular Oral and Subglottal Pressure Signals from Hertegård, Gauffin & Lindestand (1995). Example of the location used to estimates subglottal pressure from oral pressure. The location used to estimate subglottal pressure is denoted by the middle dashed vertical line. The shape of the oral pressure signal is rectangular. Adapted from A comparison of subglottal and intraoral pressure measurements during phonation, by S. Hertegård, J. Gauffin, and P. A. Lindestad, 1995, Journal of Voice, 9(2), p As the ideal shape of the oral pressure signal is rectangular and equal across adjacent oral pressure plateaus (because this should guarantee that the subglottal pressure is constant throughout the utterance), the mid-point along the plateaus would be an appropriate location to estimate subglottal pressure. However, there is a need to study how the flat plateau is NOT achieved, and also if there is a peak rather than a plateau. If the oral pressure profile has a peak, it is important to determine whether the peak equals the more accurate plateau value or either underestimates or overestimates the subglottal pressure. Hertegård, Gauffin, and Lindestad (1995) presented an example of a peaked or sloped up to the end portion of /p/ occlusion shaped pressure signal (Figure 1.5). Again the authors found that when comparing the actual subglottal pressure to the oral pressure, the most accurate location for pressure estimates was the beginning of lip occlusion for the /p/ (Hertegård, Gauffin, & Lindestad, 1995).

26 15 Figure 1.5. Non-rectangular Oral and Subglottal Pressure Signals from Hertegård, Gauffin & Lindestand (1995). Example of the location used to estimates subglottal pressure from oral pressure for a non-rectangular shaped oral pressure. The location used to estimate subglottal pressure is denoted by the middle dashed vertical line. The location used to estimate subglottal pressure is the same for the rectangular shape as it is for the shape presented herein. Adapted from A comparison of subglottal and intraoral pressure measurements during phonation, by S. Hertegård, J. Gauffin, and P. A. Lindestad, 1995, Journal of Voice, 9(2), p Figure 1.6 shows a variety of shapes of the oral pressure signal that occur based on varying physiology (the profiles are concatenated together from different utterances). The first syllable depicts the ideal pressure shape (rectangular). The location of the arrow in the first syllable indicates the oral pressure that is assumed to be equal to the subglottal pressure during the following vowel. In the next two syllables, the height of the pressure signal is approximately equal to the height of the pressure signal in first syllable. This would suggest that the location of the arrows on the pressure signal in the second and third syllable would provide a correct estimate of the subglottal pressure during the vowel, but some variation of pressures is occurring so that the pressure signal is not completely flat on top. In the fourth and fifth syllable the indicated location of measurement does not have the same amplitude (lower and higher, respectively) as the initial syllable (which is assumed to be the true pressure), and thus the

27 16 measurement location (and the shape of the pressure signal) would not be appropriate to use to estimate the subglottal pressure from the oral pressure. Figure 1.6. Various Oral Pressure Signal Shapes. This figure shows a concatenation of various oral pressure signal shapes. The problem of the location of measurement arises when the shape varies. The arrows in the figure show potential measurement locations. If we assume that the first pressure signal depicted is an accurate estimate of subglottal pressure, then the measurement location of the next two syllables is correct because the oral pressure is nearly the same as the oral pressure in the first syllable. However, the estimate of subglottal pressure from oral pressure for the last two syllables would be in error because the oral pressure is lower and higher, respectively, than the oral pressure of the initial profile. Equipment calibration and frequency response. Consideration needs to be given to the equipment used to collect recordings. Solomon and Helou (2013) emphasize that the pressure transducer must be well calibrated with an accurate zero baseline, as measures of pressure will be erroneous with miss-zeroed baselines. Rothenberg (2013) suggested that the majority of the errors in intraoral pressure recordings stem from inadequate pressure transducer equalization time. He proposed that 25 ms should be the maximum length of time required for the system to respond to pressure changes; this suggests a flat frequency response to 40 Hz (i.e., 1/0.025s). Specific Purpose of the Current Study Although research has been done to support the use of oral pressure during lip occlusion to estimate subglottal pressure, the literature presents a knowledge gap in regard to specific

28 17 variations in accuracy of estimates that can occur. This study looked at six characteristics that may affect the estimates of subglottal pressure using the oral pressure approach during the typical syllable repetition task: (1) syllable rate, (2) lip occlusion closed quotient (Kitajima & Fujita, 1990), (3) voicing of initial consonant (/p/ vs /b/), (4) misarticulations of initial consonant (/p/ vs. / /, a bilabial fricative), (5) modeled velar leak, and (6) two syllable repetition task (Table 1.2). It is hypothesized that variations within these characteristics (while the subject is using equal effort for each production) may create significantly altered oral air pressure waveforms, and thus create confounding issues for accurate subglottal pressure estimates. For this study, the standard for which accuracy is assumed is smoothly produced /p:i:p:i:p:i:p:i:p:i:/ strings at approximately 1.5 syllables per second and approximately a 50% lip closed quotient with pressure pulses having flat plateaus of equal height across the syllable string. The results of this project provided important information leading to better practice methods for estimating subglottal pressure, an important component of acquiring phonatory aerodynamics in clinical and research settings. Table 1.2. Experimental Tasks Part Standard Production Experimental Condition Condition Part 1 No Untrained Part 2 Yes Faster rate and varying lip closed quotient /p:i:p: / Part 3 Yes Voiced consonant /b:i:p: / Part 4 Yes Bilabial fricative / :i: / Part 5 Yes Velar leak /m:i:m: / Part 6 Yes Two syllable production /pip / List of experimental tasks for each part. Standard production condition was not used in Part 1 and is indicated by No in the table.

29 18 METHODS Subject Selection Ten subjects, five adult males and five adult females, were selected based on their ability to complete the required tasks. A medical history (pertinent to voice and speech) was obtained (Appendix A). Each subject was given a hearing screening (audiometers: MAICO MA 25 Audiometer, Serial #39357; MAICO MA 42 Audiometer, Serial #22881; Beltone Special Instruments 120 Audiometer, Serial # ) at 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz at 20 db. The Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) (Appendix B) (Kempster, Gerratt, Verdolini-Abbott, Barkmeier-Kraemer, & Hillman, 2009) was also given to each subject by a licensed speech-language pathologist. All subjects were between the ages of 20 and 40, native speakers of English, and non-smokers. Exclusion criteria included the person having had a recent voice and speech problem or the person being currently ill. Table 2.1 presents the demographic information and the inclusion criteria results for each subject. Table 2.1. Demographics of Subjects Subject Gender Age CAPE-V Overall Severity Rating Hearing Screening Results Voice and Speech Questionnaire Results Used In Current Study M1 Male 27 1/100 Pass Pass yes M2 Male 24 1/100 Pass Pass yes M3 Male 27 30/100 Pass Pass no M4 Male 24 11/100 Pass Pass yes M5 Male 35 0/100 Pass Pass no F1 female 36 0/100 Pass Pass no F2 female 20 0/100 Pass Pass yes F3 female 23 0/100 Pass Pass no F4 female 20 0/100 Pass Pass yes F5 female 29 3/100 Pass Pass yes Demographic information for 10 subjects recorded. 6 subjects were used in the current study and 4 were not used, despite all subjects meeting inclusion criteria.

30 19 Equipment The Glottal Enterprises aerodynamic system (MSIF-2 S/N 2049S) was used in this study. The system includes a clear facial mask with holes covered with mesh wire, a thin tube attached to a pressure transducer (Glottal Enterprises MSIF-2 S/N 2049S) that goes through the mask and sits just inside the mouth just past the lips (for oral pressure recordings) and another pressure transducer for measurement of trans-mask air pressures that were calibrated to airflow through the mask. This system was calibrated using constant flow and constant pressure techniques (see Appendix C and Appendix D, respectively). The response time of the pressure transducer for measuring the oral pressure was determined in order to test whether it should follow the physiological production of the oral pressure faithfully. The response time was measured by the following process. An inflated balloon (un-inflated: 6 cm long by 2 cm wide; inflated: 13 cm long by 7 cm wide) was placed over the oral pressure tube which was connected to the pressure transducer. This was performed by using the fingers of one hand. The pressure signal was given time to stabilize. The air was then quickly released from the balloon by releasing the seal of the neck of the balloon at the base of the oral pressure tube by pulling the fingers outward, thereby rapidly decreasing pressure inside the balloon. The length of time from a deviation in the flat portion of the positive pressure to a return to the flat portion of the pressure signal (now at atmospheric pressure) was measured and is reported as the response time. The response time of the pressure transducer used in the current study was measured to be approximately 10 ms using the method just discussed (see Figure 2.1). The actual response time may be shorter as the technique used to measure the response time of the system may result in a longer length of time of air pressure release than in traditional techniques (i.e., balloon burst technique). It is noted that the response time needed to

31 20 show pressure changes created by lip closure during variations of the pressure signal is around ms (see Figure 3.2), well within the response time of the pressure transducer system, which therefore should follow oral pressure changes faithfully during the experiment. Figure 2.1. Response Time of Pressure Transducer. This figure shows the pressure signal during the balloon air release technique to determine the response time of the pressure transducer used to record the oral pressure. The flat portion at the beginning of the signal is just before the release of air from the balloon. The flat portion at the end of the signal is after the system has returned to atmospheric pressure. The response time is measured from corner to corner. In this example, the response time is 8 ms. A microphone system (Radio Shack Omnidirectional Tie Clip Microphone Model with a frequency response of 50-16,000 Hz) was used to record the audio signal. The microphone was mounted to a head set to ensure a constant mouth to microphone distance for all subjects. This signal was used to monitor consistency of signal amplitude and intensity across breath group tokens (via analysis using Praat software and custom software SIGPLOT written in Matlab code). During the experiment the operator determined via the digital oscilloscope whether the audio signal had relatively constant amplitude. An electroglottograph (Kay Elemetrics EGG, Model 6130) was used to obtain the EGG signal for future analysis (such as the

32 21 consistency of glottal closed quotient and magnitude of the EGG waveform across the breath group tokens). A 16 bit DATAQ A/D converter system (Model DI-720 Series) with Windaq software was used to digitize the simultaneous audio, pressure, flow, and EGG signals into computer files at 20,000 samples per second for each channel. Standard Production Condition The basic approach in this study was to use a standard production condition that has a high probability of accurate estimation of the subglottal pressure (see Figure 1.2). That condition was the /p:i:/ syllable string produced (1) smoothly, (2) at a comfortable and constant effort level, (3) at a rate of approximately 1.5 syllables per second, (4) with lips closed for about half of the syllable duration (50% lip closed quotient), and (5) with flat pressure plateaus indicating pressure equilibration throughout the entire airway during the lip occlusion. As conditions are altered parametrically away from the standard, the pressure pattern during the lip occlusion may vary. It is this variation of shape and size that was investigated, with emphasis on the location and value of the maximum pressure. Method Used to Estimate Subglottal Pressure from Oral Pressure The literature suggests several methods for estimating subglottal pressure from oral pressure. A common method is to take the peak oral pressure of a consonant before and after a vowel and connecting those points with a line. From that line, a vertical line would be created at the midpoint of the vowel. The pressure value at the location where the vertical line touches the line connecting the peaks would be the estimate of subglottal pressure (e.g., Smitheran & Hixon,

33 ). In contrast, Hertegård, Gauffin, and Lindestad (1995) take the first moment of occlusion before and after the vowel and connect those points with a line. The vertical line would be drawn at the midpoint of the vowel with the location where the vertical line touches the line connecting the occlusion points would be the estimate of subglottal pressure. They argue that this method is appropriate because the shape of the oral pressure occlusion should be rectangular not peaked (see Figure 1.4) (Hertegård, Gauffin, & Lindestad, 1995). In the current study, the average from the moment of full lip closure to the moment the lips separate was obtained for both occlusions surrounding a vowel. That is, the pressure signal and the timing aspects of the recording from SIGPLOT were written into a Microsoft Excel document. All data points between the time of the moment of full lip closure and the time of the moment of lip separation were averaged in Excel to get the average oral pressure for that particular occlusion. This was done for the occlusion before and after the vowel utterance. These two average pressure values were averaged to determine the estimate of subglottal pressure during the vowel. This compromise method assumes a nearly rectangular shape. This method was used for rectangular shapes, dipped pressure shapes, sloped down to the end portion shapes, and sloped up to the end portion shapes. When the shape appeared rounded or rectangular, the peak oral pressure value was taken and averaged with the oral pressure from the other side of the vowel. When the pressure shape had a pressure highest at the end portion of the occlusion or pressure at the highest at the beginning portion of occlusion, the flat portion (the portion without the sudden increase) was used for the oral pressure of that occlusion. When there was a pressure step up or step down, the highest flat portion was used as the oral pressure for that occlusion. If there is not full occlusion, there is no occlusion from which to take an accurate average.

34 23 There is concern that including the entire occlusion in the pressure average includes too much history of the pressure changes before the vowel and too much of the future of the pressure changes just after the vowel, particularly in cases where the pressure is sloped or has a pressure increase only on one corner. Based on Figure 1.5 the pressure increase that caused the pressure to be sloped up to the end portion of the occlusion was a change in pressure that was not reflected in the pressure used during the vowel (Hertegård, Gauffin, and Lindestad, 1995). Others in the literature tend to use a maximum or peak oral pressure to make estimates of subglottal pressure (Smitheran and Hixon, 1981). Based on Hertegård, Gauffin, and Lindestad s (1995) figure (Figure 1.5) the method used by Smitheran and Hixon (1981) would overestimate the subglottal pressure during the vowel. The method to estimate subglottal pressure from oral pressure in this study was used to capture the variability across all shapes and minimize errors. PART 1: Untrained Production versus Trained Production Part 1 serves to determine the impact of training on the accuracy of estimates of subglottal pressure. Past studies have reported various training methods for subjects. Smitheran and Hixon (1981) provided their subjects with a model of the target production and repeated the model each time the subject produced unacceptable productions. McHenry, Kuna, Minton, and Vanoye (1996) provided their subjects with models and practice sessions to establish the expected utterance. Hertegård, Gauffin, and Lindestad (1995) did not discuss their exact training protocol but specifically did not control for pitch. Due to the variety of training methods used, it should be beneficial to determine if subjects produce accurate estimates of subglottal pressure without training. It was hypothesized that estimates of subglottal pressure and the pressure profiles would be more varied across the utterances of the untrained productions. Based on the

35 24 literature review and pilot work, it was suspected that subjects would produce inconsistent pressures across syllables in the same utterance resulting in difficult interpretations of where to estimate subglottal pressure. Subjects might also fail to keep the lips together or the velum raised, resulting in flow leaks, potentially lowering the estimates of subglottal pressure. For Part 1, the untrained productions were recorded (after equipment testing was conducted). [Note that in this Part both untrained and trained productions are reported, where the trained productions were those from the trained standard production condition recorded in Part 2.] The aerodynamic mask system and EGG electrodes were used during this Part 1. Prior to recording the untrained productions, the subjects were read the following instructions: You should put the mask on your face, take a normal breath, and say the required utterance. When you are told, place the mask flush against your face and say peep 9 times on one breath as smoothly and evenly as you can. The subject repeated this task five times and the recordings were compared to the recordings of two standard production condition tasks recorded in Part 2. The estimated subglottal pressures, rate, and lip closed quotients were compared between the untrained and trained productions to determine if training subjects improves the estimates of subglottal pressure. PART 2: Rate and Lip Closed Quotient Part 2 serves to examine syllable rates and lip closed quotients for producing accurate estimations of subglottal pressure from the oral pressure. The syllable rate should not be so fast that pressures cannot equilibrate, nor so slow that the subject is prone to alter lung pressures (i.e., lack of using a constant lung pressure). The lip closed quotient (percentage of time during the syllable that the lips are together) also must not be so short that pressures have insufficient time

36 25 to equilibrate nor so long that there is insufficient time to produce the vowel itself. The successful syllable rates and lip closed quotients should allow for constant velar closure, because lack of velar closure creates a flow leak into the nose and oral pressures may be below the value of the subglottal pressure (Smitheran & Hixon, 1981). The most commonly used syllable rate target is 1.5 syllables per second, but the necessity of defining a lip closed quotient has apparently not been discussed in the literature. For Part 2, the subjects were trained to produce the standard production condition first. The full training protocol can be found in Appendix E. The focus of the training protocol was to produce oral pressure signals that had flat plateaus during the /p/ lip occlusion. The subjects were then taught to speed up their syllable production rate up to the fastest they could, but with the same amount of lip compression, the same loudness, and at a constant pitch (using the same amount of production effort). Finally, the subjects were taught to smoothly move from their fastest syllable rate to the standard syllable rate. Each of these components was combined so that after a single inhalation the subject began by producing several syllables in the standard production condition, moving to their fastest syllable production rate, and ending with several syllables again in the standard production condition. The subjects were told to use a normal loudness and effort, which should have created a certain relatively flat peak-to-peak amplitude of the audio signal (as well as a flat amplitude for the other signals the flow and EGG waveforms during the vowel production). The subjects were trained to maintain the same loudness (viewed as a constant audio signal amplitude). [In a future analysis, the EGG signal should reveal whether glottal closed quotients also remained the same.] Once properly trained, the subjects used the aerodynamic mask system to obtain air flows and oral pressures for the tasks. The tasks were produced five times.

37 26 The researchers attempted to monitor the flow signal to ensure that no air was leaking through the nares during the consonant occlusion, as this may create an inaccurate estimate of subglottal pressure. When this occurred, the subjects were instructed and further trained to keep their velum up while producing the syllable string. For this experiment, the lip closed quotient and syllable rate were measured at three instances, namely during three consecutive standard syllables (not including the first syllable produced), the fastest three consecutive syllables produced (not including the first and last syllables of the faster set), and the last three consecutive standard syllables produced (not including the last syllable produced). Compared to the standard (1.5 syllables per second, 50% LCQ), it was hypothesized that faster rates and varied lip closed quotients would produce pressure pulses without flat plateaus but with relatively sharp peaks that would have less amplitude than the standard case (lower estimates of subglottal pressure). Figure 2.2 shows a sample recording of this experiment. During the same exhalation, the subject increased the syllable rate from the standard production condition to the fastest syllable rate he could manage. The subject then slowed the syllable rate back to the standard production condition. The syllables chosen for analysis in the three productions are indicated in the figure. The difference in estimated subglottal pressure from the fastest syllable rate to the syllables of the standard production conditions was a 3% difference in this example.

38 27 Figure 2.2. Oral Pressure Signal from Part 2. This figure shows an example of the oral pressure signal for Part 2 from a pilot study subject. The syllables chosen for analysis are marked. In the figure, the estimated subglottal pressure is just slightly less on average for the standard production condition than for the fastest syllables (3% difference). The pressure peaks for the standard production syllables are more plateau shaped, while the pressure peaks for the faster syllable rates are less rectangular and more peaked. PART 3: Initial Voicing Part 3 examined the effect of using the voiced consonant /b/ as the initial consonant and thus the smoothly produced syllable string /bi:p:bi:p: / for the estimation of subglottal pressure from oral pressure. It was hypothesized that the syllable string /bi:p:bi:p: / would give estimations of subglottal pressure that were accurate because the lack of aspiration reduces physiological interactions. In addition, it might reduce local pressure changes on the plateau of the pressure pulses attributed to aspiration. The subjects were requested to produce /p:i:p: / strings followed by /bi:p: / strings and then /p:i:p: / strings again during the same breath group (exhalation) in a legato manner at a rate of approximately 1.5 syllables per second and a 50% closed quotient. That is, the subjects were requested to produce the syllable string /p:i:p:i:p:i:p:i:bi:p:bi:p:bi:p:bi:p:bi:p:p:i:p:i:p:i:p:i:/ on one breath group. Equal respiratory effort was to be used for all syllables within the string. The task was produced five times by each subject. The syllable rate and lip closed quotient were measured to ensure they were near the

39 28 standard production condition. The subglottal pressure was estimated for the middle two vowels of the middle two syllables of each syllable set. The difference between the estimated subglottal pressure for the /b/ and /p/ syllable was calculated. Pilot work indicated that when using approximately the standard production condition (in the pilot example, 1.35 syllables per second with a 47% lip closed quotient was produced, whereas the target standard is 1.5 syllables per second with a 50% lip closed quotient), there was little difference (approximately 3% difference) between the estimated subglottal pressure during the occlusion between the voiced and unvoiced initial consonant syllables. For the male subject of this pilot run, when the syllable rate was increased to 3.38 syllables per second (49% lip closed quotient), the difference in oral pressures between the initial /p/ syllables and /b/ syllables increased to approximately a 9% difference. When the subject increased to a syllable rate of 5.13 syllables per second (60.4% lip closed quotient), the difference between /b/ and /p/ productions changed to -6% difference. Thus, in this case, when the syllable rate increased to the fastest rate, the subglottal pressure estimate for the /b/ syllables increased to a greater value than the /p/ syllables. The pilot study suggests that when the syllable rate increases to a certain rate, voicing of the consonant may be difficult to turn off. This is seen as voicing on the pressure signal. This voicing on the pressure signal increases the difficultly of determining an appropriate location to measure intraoral pressure (see Figure 2.3).

40 29 Figure 2.3. Oral Pressure Signals Comparing /b/ and /p/ as Rate Increases. This figure shows an example of the difference in subglottal pressure estimates (from a normalized subglottal pressure value) for initial /b/ and /p/ as the syllable rate increases (pilot study results). As the syllable rate and lip closed quotient increased, the difference between the pressure for /b/ and /p/ changed in this example (increased pressure for /bi:/ for 3.38 syl/s and decreased for /bi:/ for 5.13 syl/s). The voicing can be seen to continue onto the pressure signal of /p/ to a lesser degree and /b/ to a greater degree for the bottom trace where the syllable rate is the fastest. The length of time of lip closure was consistently around 0.05 s for the /p/ syllables while the lip closed time for the /b/ syllables decreased from 0.08 s to 0.05 s as the syllable rate and lip closed quotient increased. PART 4: Misarticulations Part 4 examined the effects of bilabial misarticulations on the estimates of subglottal pressure from the oral pressure. The hypothesis was that when a subject moves from a bilabial to a bilabial fricative initial consonant, imitating an inadequate lip closure during the intended /p/, the oral pressure and thus the estimation of subglottal pressure will reduce due to an inadequate buildup of oral air pressure (and thus lack of equalization of air pressure from the lungs to the oral cavity) during the consonant lip occlusion. It was expected that the change of oral pressure would be similar to the difference between /pv/ syllables and /fv/ syllables found in the literature. Arkebauer, Hixon, and Hardy (1967) found that the mean peak intraoral pressure decreased 1.78 cm H2O in ten children. Similarly, Subtelny, Worth, and Sakuda (1966) found a

41 30 mean oral pressure decrease of.63 cm H2O (standard deviation = 1.25 cm H2O) for males, 1.18 cm H2O (standard deviation = 3.66 cm H2O) for females, and 1.71 cm H2O (standard deviation = 4.53 cm H2O) for children. Alternating from the /p:i:p / syllable to the / :i: / syllable introduces a flow leak between the lips during the / :i: / string rather than a full vocal tract occlusion. In the recording, the subject alternated between /p:i:p / and / :i: / strings on one breath group (/p:i:p:i:p:i:p:i:f:i:f:i:f:i:f:i:p:i:p:i:p:i:p:i:/ in a smooth legato fashion with equal effort throughout. Before recording, the subject was trained to correctly produce the / :i: / syllable as a bilabial fricative around the oral tube. Standard conditions of smoothness, comfort level, effort level, and rate were used. The task was repeated five times by each subject. The syllable rates and lip closed quotients were measured to ensure they both fell near the standard production condition. The subglottal pressure was estimated for the middle two vowels of the middle two syllables of each syllable subset. The difference between the estimated subglottal pressure for the /p/ and / / syllables was calculated. Pilot work indicated that the / :i:.../ syllables had approximately 29% lower pressure peaks than the /p/ syllables. The shape of the / :i: / syllables were also sloped down to the right, making it difficult to determine the most accurate location to make a pressure measurement. Figure 2.4 shows the difference between a /p/ and / / syllable. Figure 2.4. Oral Pressure Signal Comparing /p/ and / /. This figure shows the oral pressure of two /p:i:/ syllables and two / :i:/ syllables from the pilot work. The pressure peaks for the / :i:/ syllables are approximately 29% lower than for the /p:i:/ syllables and show an alternate shape from the standard rectangular shape.

42 31 PART 5: Velar Leak Part 5 determined how large the effect and the direction of the effect that an imitated velar leak has on the estimate of subglottal pressure from oral pressure. The nasal consonant /m/ was used to imitate a large velar leak in this experimental condition. The increased flow during the nasal consonant was evidence of the velar leak. When a velar leak or an imitated velar leak (as in this experiment) occurs, the estimated subglottal pressure may be reduced because the escape of air through the velopharngeal port may prevent full pressure equilibration, resulting in an upper plateau in the pressure signal that is lower than if the leak were not occurring, or perhaps the lack of a pressure plateau. Studies have shown that the intraoral pressure for /m/ versus /p/ is dramatically less due to the open velopharyngeal port (Subtelny, Worth, & Sakuda, 1966), and a large difference was also expected here. Of further interest here is the shape of the oral pressure signal during the /m/ lip occlusion compared to the /p/ lip occlusion. The experimental task required the subject to alternate between /p:i:p / and /m:i:m/ on one breath group forming the utterance /p:i:p:i:p:i:p:i:m:i:m:i:m:i:m:i:p:i:p:i:p:i:p:i:/. While producing the /m:i:m/ syllable the lips were to be completely closed during the /m/ consonant. The subjects were trained to use constant pitch, rate, effort, lip closure pressure, smoothness, and loudness. The standard syllable rate (1.5 syllables per second) and lip closed quotient (50% lip closed quotient) were to be approximated by each subject. The task was produced five times by each subject. The syllable rates and lip closed quotients were measured to ensure they both fell within the standard production condition. The subglottal pressure was estimated for the middle two vowels for the middle two syllables from each syllable subset of four. The difference between the estimated subglottal pressure for the /p/ and /m/ syllables were calculated.

43 32 Pilot work suggested that the value of the estimated subglottal pressure during the /m/ syllables is approximately 44% lower than that of the /p/ syllables. Across the pilot recordings, the shape of the oral pressure signal for the /m/ syllable varied significantly, but always with the lowest pressure in the middle, resulting in a dipped shaped pressure signal. This shape is evident in the first /m/ syllable and the final two /m/ syllables in Figure 2.5. Consistently after the /m/ lip opening, the oral pressure dropped below baseline. This would be due to a lower pressure value in the closed pressure system possibly due to an expansion of the oral cavity as the velum rose before the production of the vowel. The variation of the oral pressure shape and magnitude during the /m/ productions suggests a variation of the flow resistance of the velopharyngeal port as well as vocal tract volume variation. For example, the reduction in pressure during the /m/ of the first two /m/ syllables may be due to a change in velopharyngeal flow resistance, being less for the first /m/ consonant. The varied shape may be a result of the amount of air allowed to leave through the velopharyngeal port, the amount of lip compression used, and/or the degree of lip closure. Multiple signals should be analyzed to determine the exact cause of the changes in the oral pressure signal for the /mi:/ syllable. Figure 2.5. Oral Pressure Signal Comparing /p/ and /m/. This figure shows the oral pressure signal during the pilot work comparing the syllables /p:i:p: / and /m:i:m: /. During the /m:i:m: / syllable there is increased voicing continuing during the lip closing phase (left side of the pressure rise). During the lip opening phase, the pressure drops below baseline before rising to the next consonant during the vowel. This suggests an increase in the vocal tract volume, perhaps due to the velum rise, just before the vowel is produced. The shape of the pressure signal during the /m/ syllables varied greatly across pilot runs, but the amplitude of the pressure during the consonant was never as great as the amplitude of the pressure during the /p/ syllables.

44 33 PART 6: One Syllable versus Two Syllables Part 6 studied the effects of using a two syllable production with /p/ consonants on the estimation of subglottal pressure from oral pressure. The two syllable production was similar to pepper, as suggested by Rothenberg (2013). If there were sufficient rise time for the oral pressure during the lip occlusion, the asymptotic oral pressure should represent the subglottal pressure well. However, a two syllable production such as pepper has a stressed first syllable and an unstressed second syllable. If the goal is to estimate the subglottal pressure during the inter-consonantal vowel, a changing lung pressure due to linguistic stress may not allow accurate subglottal pressure estimations (Netsell, 1973). In this experiment, the two syllable production peeper was used because the /i/ vowel matches the vowel of the standard syllable. The subject alternated between /p:i:p:i: / and /pi:p pi:p / on the same recording. Namely, the subject produced /p:i:p:i:p:i:p:i:p:i:pi:p pip pip pip pip p:i:p:i:p:i:p:i:p:i:/ strings on one breath group, where the duration of the two syllables /pip / was the same as that for the single syllable /p:i:/. The subject used approximately the standard production condition (smooth, constant effort, 1.5 syllables per second, 50% lip closed quotient) for the /p:i:p: / syllables. While producing the two syllable production peeper the subject was instructed to think of it as a single unit, that is, the second syllable should be considered to be less stressed (de-stressed), but with the first syllable of the same stress as used for the /p:i:p: / syllables. The task was repeated five times by each subject. This experiment was used to gain further understanding of the difference between the oral pressure during lip occlusion during the /p:i:p: / string when compared to the peeper strings. It was hypothesized that the pressure during the /p/ s during peeper would be higher

45 34 without a plateau (i.e., more pointed) because of the transition from a stressed syllable to an unstressed syllable. Pilot work suggested that the subglottal pressure may be more difficult to estimate for the two syllable production because the shape of the pressure signal varied based on the stress placed on the first syllable in the two syllable production (see Figure 2.6). The upslope of the oral pressure during the /p/ before the stressed vowel (the pressure top increased to the right) appears to lead to the higher starting pressure of the /p/ at the end of the stressed vowel (before the unstressed vowel). This suggests that the best approximation of the subglottal pressure during the stressed vowel is an average between the last oral pressure before the stressed vowel and the first pressure after the stressed vowel, and thus the average between the two oral pressure peaks before and after the stressed vowel. This strategy may not be best for all subjects, so examination of the experimental recordings may lead to more plausible assumptions and analyses. The subglottal pressure will thus be estimated for the /i/ vowel of both the syllable string and the stressed vowel of the two syllable production. The amount of pressure difference between the two syllable productions and the single syllable production will be calculated. Pilot work suggests that this change is only approximately 3% when using the calculation just discussed for the pressure of the stressed vowel in the two syllable production. It is noted that the higher pressure during the /p/just before the second syllable in peeper suggests that the first syllable stress also involves pitch rise as well as loudness (subglottal pressure).

46 35 Figure 2.6. Multi-signals for /p:i:p:/ and /pip /. This figure shows the recorded signals from the pilot work of three /p:i:p/ syllables and three repetitions of the two syllable production peeper. The overall oral pressure for the two syllable productions decreased with each word that was said, while the pressure for the syllable repetition remained constant across the syllables produced. The pressure shape (PRS) for the two syllable productions was influenced by the stress placed on the first syllable, resulting in the oral pressure of the /p/ before the /i/ to be sloped upward to the right and the pressure of the /p/ after the /i/ to be sloped downward. The pressure peak following the stressed vowel is also slightly higher on average than the pressure peak before the stressed vowel. It is noted that the peeper production was spoken in the same amount of time as one syllable of /p:i:p/. Analysis A sign test was conducted to determine the direction or sign of the difference between the two related measures (Siegel & Castellan, 1988). Namely, for this study, the average of two subglottal pressure estimates from the experimental condition was subtracted from the average of the subglottal pressure estimates of four standard production conditions. The null hypothesis for all experimental tasks was that there was no difference in subglottal pressure estimates between the standard production condition and the experimental task at hand. A one-tail probability test

47 36 RESULTS AND DISCUSSION Construct of a Pressure Signal Pilot work suggested that it is instructive to consider the oral air pressure signals during the lip occlusion task as having two main portions, namely, a lip closure gesture and a lip opening gesture. It is emphasized that these two gestures are actually oral pressure changes, and the closing motion and closed position of the lips are inferred; there were no actual measures of lip activity in this study. During the lip closure gesture there are three main segments of the pressure signal (Figure 3.1). The mean oral pressure during the vowel is near atmospheric pressure just prior to vocal tract occlusion initiation. The first segment on the oral pressure signal is an acoustic transition which occurs after initiation of occlusion of the vocal tract at the lips while acoustic co-articulation is occurring. In this segment the vocal folds are still vibrating while glottal abduction is taking place (Löfqvist & Gracco, 1997), and the acoustic pressure cycles are superimposed upon the rise in the mean pressure signal within the oral cavity due to the vocal tract occlusion and constant lung pressure. The second segment of the gesture is a continuation to full pressure equilibration where the remaining pressure rises toward maximum. This latter phase may or may not occur with continued laryngeal vibration, and the assumption is that vocal tract occlusion at the lips is complete. When the initial consonant is voiced, as in the /bi:p:/ syllables, the acoustic signal is more noticeable on the intraoral pressure signal in both the first and second segment of the gesture. Despite the increased influence of the acoustics on the pressure signal, Löfqvist and Gracco (1997) found that voicing of the stop consonants does not consistently impact timing aspects of lip or jaw movement. The third segment is continuation of complete equilibration. This is commonly known as the top portion of the oral pressure signal.

48 37 This can occur with a variety of pulse shapes (to be discussed and shown below). The ideal shape is rectangular or a flat plateau shape of complete equilibration during the lip occlusion. Shipp (1973) suggests that the lips become completely sealed within plus or minus 4 ms of the steep rise in oral pressure for a bilabial stop consonant. Figure 3.1 shows each segment of the pressure during the lip closure gesture. Timing aspects (particularly for the acoustic transition and pressure equilibration phases) and feature presentation (i.e., amplitude of the voicing signal during the acoustic transition) of these portions may vary based on the experimental conditions. Figure 3.1. Lip Closure Gesture on Oral Pressure Signal. The upper portion of the figure shows one syllable of speech plus the lip occlusion of the following syllable. The syllable rate of this recording is 1.3 syllables per second with a 44% lip closed quotient. The lower portion of this figure shows the three main segments of the pressure signal during the lip closure gesture. In this figure, the acoustic transition time is 27 ms and the pressure equilibration time is 14 ms, creating a total pressure rise time of 41 ms. The shape of the full equilibration is rectangular. Note: The pressure scale is arbitrary. In the current study, the duration of pressure rise during lip closing was measured for the standard production condition and faster condition from Part 2. In Figure 3.1, the duration of pressure rise during lip closing is equal to the time of acoustic transition with pressure rise plus

49 38 the time of pressure equilibration (time of 1 plus time of 2). These measures were only able to be made when the pressure fully equilibrated (as noted by rectangular shaped oral pressure signal and flow reaching zero during the /p/ occlusion). For one subject (F5) the faster conditions from three recordings never fully equilibrated so duration of pressure rise during lip closing could not be calculated. The average duration of pressure rise during lip closing for the standard production condition for all subjects was ms (range: ms to ms) and the average duration of pressure rise during lip closing for the experimental condition for all subjects was ms (range: ms to ms) (Figure 3.2). The figure indicates that there is no strong relationship between syllable rate and duration of pressure rise during lip closing. The closing duration range is relatively wide during the standard production condition of less than 2 syl/sec (approximately 30 to 80 ms), whereas for faster syllable rates, the range is narrower (approximately 35 to 60 ms).

50 39 Figure 3.2. Syllable Rate v. Duration of Pressure Rise During Lip Closing. The rate versus duration of pressure rise during lip closing for all subjects for the standard production condition and the faster condition from Part 2. The standard production condition rates are all below 2 syllables per second and the faster condition rates are all above 2 syllables per second. There does not appear to be a relationship between rate and duration of pressure rise during lip closure. The continuation of full equilibration portion of the oral pressure signal is followed by the lip open gesture of the oral pressure signal, having two basic segments (Figure 3.3). The first segment is when the oral pressure begins to fall without phonatory acoustics visible on the pressure signal because the vocal folds have not begun vibrating while the lips begin to separate (adduction is not yet sufficient to begin phonation, apparently). Sometime during this segment, however, voicing may appear as mean pressure continues to fall. Löfqvist and Gracco (1997) indicated that the vowel following the consonant has an impact on the lip opening gesture, particularly that of the lower lip and jaw movement. Notably, the position of the lower lip at the beginning of the lip opening gesture was lower for /u/ than /i/ and lower for /i/ than for /a/ (Löfqvist & Gracco, 1997). This may suggest that the time it takes for the lip opening gesture to

51 40 occur, particularly the duration of the first segment, may be reduced for /u/ compared to /i/ and /i/ compared to /a/. The first segment extends to the baseline. During the second segment, the oral pressure is near atmospheric pressure and the vowel following the lip occlusion is produced. The return of the oral pressure to baseline corresponds to complete lip separation (Hinton & Luschei, 1992). This vowel is in the same syllable as the consonant just analyzed. Notice that the pressure fall segment during the lip opening segment happens more quickly than the pressure rise segment during the lip closing phase. This is most likely due to lip motion mechanics. Löfqvist and Gracco (1997) found the velocity of the lips is greatest during the lip closing gesture, particularly the velocity of the lower lip, which is found to compress into the upper lip at its greatest velocity. However, from a pressure release point of view, lip opening may create faster oral pressure change (reduction) because pressure is being released by relatively simple lip separation to immediately decrease the pressure to the atmospheric value, rather than built up by more complex articulatory motion to reach a pressure plateau determined physiologically.

52 41 Figure 3.3. Lip Open Gesture on Oral Pressure Signal. The upper portion of the figure shows one syllable of phonation and the lip occlusion of the following syllable. The syllable rate of this recording is 1.3 syllables per second with a 44% lip closed quotient. The lower portion of this figure shows the two portions of the lip open gesture. Notice that the first segment in this example, where oral pressure decreases, has no acoustic pressures riding on the mean pressure drop, although in other tokens there may be acoustic variation due to phonation. The second segment of the lip open gesture is the duration at baseline when the vocal tract is open and the pressure is approximately atmospheric, a portion of which is seen in the figure. The time for the lip opening phase (the first segment) is 19 ms. Note: The pressure scale is arbitrary. Pressure Shapes Table 3.1 presents the primary oral pressure signal shapes during lip occlusion seen in this study. Any change in pressure is the result of a change in the volume of the vocal tract (an increase in pressure is the result of a decrease in volume and a decrease in pressure is the result of an increase in volume) or a flow leak through the lip occlusion or velopharyngeal port. The table presents possible explanations of the changes in pressure across the /p/ occlusion.

53 42 Table 3.1. Shapes of Lip Occlusion on Oral Pressure Signals with Possible Anatomical Causes of Changes Shape Possible Causes Picture of real recording 1. Rectangular Constant pressure in the mouth; no volume changes in the vocal tract; the standard profile during lip occlusion 2. Sloped up to the end portion 3. Sloped down to the end portion Pressure building up during the lip occlusion; the volume of the airway is decreasing due to lip retraction or cheek compression, jaw movement upward, forward tongue movement, or lung volume reduction Pressure decreasing during the lip occlusion; the volume of the airway is increasing due lung volume increase, cheek expansion, lip protrusion, jaw movement downward; or slight air lead (velar, lip) 4. Pressure dip Pressure dip during the lip occlusion; the volume of the tract momentarily increases then decreases due to lung volume increase-decrease, lip retractionextension, jaw lowering-rising, lip or velar opening-closing, or cheek expansion-contraction 5. Pressure increase then stabilization Pressure increase during the lip occlusion; same as #2 with stabilization of pressure near end of lip occlusion 6. Wavy top portion Pressure variations across the occlusion; the volume of the vocal tract undergoes constant small changes due to lip, jaw, velar, cheek or respiratory movement gestures

54 43 7. Pressure highest at end portion Pressure buildup before the plosive release; same as #2 but occurring late in the lip occlusion 8. Pressure highest at initial portion Pressure buildup momentarily just after lip closure; same as #3 but occurring only at the beginning of the lip occlusion 9. Rounded Flow leak from velum or lips reduces the pressure buildup in the oral cavity; flow signal should be used to determine if this gives accurate oral pressures; could also come from a gradual vocal tract volume decrease-increase. 10. Triangular Flow leak from velum or lips reduces the pressure buildup in the oral cavity; flow signal should be used to determine if this gives accurate oral pressures; also possible fast oral volume reduction or respiratory pumping just before lip release and aspiration. 11. Pressure step down Sudden pressure decrease after lip closure; similar to #3 and #8 but with more dramatic change to an end level portion 12. Pressure step up Sudden pressure buildup before the plosive release; similar to #2 and #7 but more dramatic step upward within the lip occlusion

55 44 For some oral pressure profiles, like the triangular and rounded shapes in Table 3.1, it is impossible to determine if the pressure in the oral cavity is an accurate representation of subglottal pressure during the vowel without determining if the flow returns to baseline during the occlusion. By definition, pressure is equilibrated when the source pressure remains the same after a downstream location of the vocal tract is occluded and pressures become the same throughout. It is generally thought that a rectangular shape to the oral pressure profile is the shape in which the system has established a constant volume and the time it needs to equilibrate (Rothenberg, 2013). When the shape varies, the flow signal needs to be consulted. Figure 3.4. Multi-signals for Lip Leak/Misarticulation Condition. This figure shows the microphone, flow, pressure, and EGG signals (traces from top to bottom) for the lip leak/misarticulation condition for subject F4. The initial pressure consonant would give an accurate estimate of subglottal pressure because the lips are fully occluded, the shape has a flat plateau, and the flow returns to baseline. The next three syllables shown would give pressure estimates that are too low because the lips do not fully occlude and the flow does not return to baseline.

56 45 Figure 3.4 presents the microphone, flow, pressure, and EGG signals (from top to bottom) for the lip leak condition or misarticulation condition. The first and last syllables are part of the standard production condition and give an accurate estimate to the subglottal pressure. They are thought to be accurate because the flow returns to baseline during the /p/ lip occlusion (denoted by an arrow in the figure for the first one) and have a relatively flat plateau. When a lip leak is present, the lips never fully occlude (evidenced by the rounded shape to the pressure signal) and the system never equilibrates (evidenced by the flow not returning to baseline during the attempt to occlude the vocal tract and by the reduced pressure peaks). This figure is a good example of how the flow helps to determine if equilibration has occurred. When examining the pressure signals of the lip leak syllables, they at first may appear to have a similar oral pressure value as the surrounding standard production condition pressure. Without the flow, these pressures might have been used to estimate the subglottal pressure from the oral pressure. This estimate would be too low and thus inaccurate, however, because the vocal tract has not experienced pressure equilibration. The oral pressure is not giving an accurate estimate of what is happening below the vocal folds. Figure 3.5 shows the pressure and flow for the example presented in Figure 3.4 in relation to what is happening in the vocal tract.

57 46 Figure 3.5. Vocal Tract Configuration, Oral Pressure, and Oral Flow for Lip Leak/Misarticulation Condition. The top image shows the vocal tract first during a /p/ lip occlusion where the lips are closed and the glottis is open, creating an equilibrated vocal tract (rectangular pressure signal, middle, and zero baseline flow, bottom). During the vowel, shown in the second vocal tract image, the lips are open and the vocal folds are vibrating to produce voicing. Finally, the top image shows the vocal tract during an occlusion with a lip leak. The lips are slightly separated resulting in non-zero DC flow and a non-rectangular (rounded) oral pressure shape. An estimate of the subglottal pressure for the vowel would be inaccurate because the true oral pressure during the second consonant is too low. PART 1: Untrained Production versus Trained Production The first set of recordings made by each subject was a recording that was conducted without instruction regarding how to produce flat topped pressure signals. The estimated subglottal pressure of two vowels from the untrained task were compared to the estimated subglottal pressure of two vowels from the second standard production condition of the Part 2 recordings. Recordings from subject F4 were excluded from the analysis because the oral pressure during the vowel did not return to zero, indicating that the oral pressure tube had a collection of saliva that prevented accurate pressure measurements. For the untrained condition, the average rate across all subjects was 1.79 syllables per second (range: 1.19 to 2.26 syllables per second) compared to an average rate of 1.56 syllables per second (range: 1.21 to 1.86 syllables per second) for the standard production condition of Part 2

58 47 recordings. The lip closed quotient for the untrained condition was 36% (range: 9% to 55%) while the lip closed quotient for the standard production condition of Part 2 recordings was 40% (range: 21% to 61%). A comparison of estimates of subglottal pressure could not be made because the standard production condition and the untrained syllables were from separate recordings. The untrained condition had the greatest percentage of syllables that sloped up to the end portion of the /p/ lip occlusion (28%) (this pattern is a positive slope of the pressure during lip occlusion; please see example 2 in Table 3.1). Other predominant shapes include a pressure step up (22%), a pressure dip during the occlusion (20%), and a rectangular shape (8%). Table 3.2 presents all the shapes for the untrained condition and the shapes of the second standard production condition of the second experimental task for six subjects. It was hypothesized that subjects, when untrained, would create inconsistent pressure across the syllables, making it difficult to estimate subglottal pressure from oral air pressure. It was also hypothesized that subjects when untrained might inconsistently have a flow leak through the velopharyngeal port or at the lips during syllable production. The sign test indicates that there was no difference between estimates of subglottal pressure for the untrained and trained conditions. Despite no statistical difference in the estimates of subglottal pressure, the subjects were more likely to increase oral pressure before the lip release noted by the high percentages of both pressure step up and pressure sloped up to the end of lip occlusion during the untrained conditions. There was no evidence of velar or lip leak during the untrained productions, hypothesized as a lower oral pressure. Furthermore, among all syllables, during the /p/ occlusion the flow returned to baseline, indicating no leaks.

59 48 Table 3.2. Shape Characteristics of Three Untrained and Three Trained Syllables for Six Subjects Untrained Condition Standard Production Condition Shape N % N % Rectangular Sloped up to the end of lip occlusion Sloped down to the end of lip occlusion Pressure dip during the occlusion Wavy flat portion Pressure highest at end portion of /p/ occlusion Pressure highest at initial portion of /p/ occlusion Rounded Triangular Pressure step down Pressure step up Occlusions containing multiple shape characteristics Note. Total number of syllables in each condition = 75 % is percentage occurrence of each shape of the total number of shapes (untrained condition n = 82, standard production condition n = 79). Occlusions that contained shape characteristics that could be categorized in more than one way are counted for both shapes. Thus, the total number of shapes in the table is greater than the total number of syllables because occlusions containing multiple shape characteristics are counted for each characteristic in the table. See Table 3.1 for definitions of the patterns mentioned in this table. The impact of training was evident on the improved shape of the oral pressure signal during the /p/ occlusion (Figure 3.6). The more rectangular shape after training increases confidence in the accuracy of the estimates of subglottal pressure because the equilibration of the vocal tract has occurred. It is again noted that the untrained syllables were not accompanied by the standard productions in one breath group so that the accuracy of the pressures could be compared. The conclusion is reached that the primary and very useful gain from training is the greater consistency of the oral pressure profile.

60 49 Figure 3.6. Comparison of Trained and Untrained Oral Pressure Signals. The first column in the figure presents a sample of the oral pressure signal from the untrained syllables from the Part 1 recordings for each subject analyzed for this thesis. The second column presents a sample of the pressure signal from the trained syllables from the Part 2 recordings for each subjected analyzed. The inconsistent shapes of oral pressure signals in the untrained conditions reduces trust in the estimates of subglottal pressure made. Training the standard production condition took varying amounts of time for each subject. Table 3.3 presents the information regarding how long it took the subject to be trained. For the first experimental task in which subjects produced the CV sequence with instructions but without training, the recordings served as a baseline for the subjects ability to produce the standard production condition and to give the researchers an indication of what changes to the pressure signal needed to be made to achieve flat plateaus. The time required to train the standard production condition (the target of which was the flat plateaus of equal amplitude across the syllables at approximately 50% lip closed quotient) varied from less than five minutes to 1 hour and 37 minutes. For Subject F1 and F4, training was stopped after the subjects were unable to successfully produce the standard production condition. Throughout the experimental tasks, many subjects needed re-training to get them back to producing the standard production

61 50 condition. All subjects needed to be reminded to produce the syllables smoothly throughout the experiment. Table 3.3. Standard Production Condition Training Information Subject Experimental Condition Part 1 Part 2 Part 3 Part 4 Part 5 Part6 M1 No training 1 hour 37 minutes M2 No training 45 minutes M3 No training 20 minutes M4 No training 5 minutes M5 No training 6 minutes F1* No training 49 minutes F2 No training <18 minutes F3 No training F4* No training 17 minutes F5 No training <5 minutes Note: Number represents number of times the subject needed to practice the utterance, the time represents the amount of time the subject was trained, and the dash - represents no data on training were collected. * represents subjects who were not able to be trained to satisfaction for the standard production condition Without training, the shapes of the oral pressure signal were more variable (see Figure 3.6). Most commonly, subjects had some gesture in the vocal tract that caused variable pressure change (i.e., pressure step down and pressure dip). The accuracy of estimates of subglottal pressure from these non-rectangular shapes is called into question. After training, most subjects were able to consistently produce rectangular oral pressure signals the majority of the time. To increase confidence in pressure estimates, it seems that training subjects or patients at least briefly is extremely important in order to better guarantee more accurate estimates. There are several subjective notes on training to be considered. Training to produce flat plateau pressures was completed using visual feedback seeing the pressure signal on a computer monitor acting as a digital oscilloscope. They could witness when their pressures did

62 51 not have flat tops and could attempt to adjust to make them flat. To become acquainted with the nature of the oral pressure and the sense of change of that pressure, some subjects were encouraged to manipulate the pressure signal by blowing gently into the tube and sucking gently on the tube. This allowed the subject to determine the sensitivity of the pressure signal and how small changes in the mouth or otherwise created large changes on the screen. Subject M1 reported knowing how the pressure signal works helps create more flat tops. Subject M2 and F4 created better flat tops when they were instructed to shut off the /i/ vowel by closing the lips into a /p/ and not changing anything else in the mouth or body. Subject M3 reported that he created better flat tops when he forcefully held his mouth shut. Training can be an important way to increase accuracy of estimates of subglottal pressure. Training the 10 individuals of this study suggests that training should be individualized to the subject or patient to insure they understand what they are doing when approximating pressure plateaus and they are able to replicate the behavior. There needs to be careful monitoring of changing the way the behavior is acquired. The experience here emphasized that the goal was to train an activity (the standard production of the CV syllables) so that subglottal pressures could be estimated, but not train activity that removed the subject from their comfortable production of sound. The training did not train unrepresentative speech behaviors. Few models of the syllable string were given to the subjects to prevent entrainment to the researchers speech characteristics. This is the pervasive assumption behind this technique shared by all researchers and clinicians. The approach taken in this study suggests that visual feedback appears to be an efficient means of helping with this training.

63 52 PART 2: Rate and Lip Closed Quotient The second set of recordings made by each subject took place after the instructions regarding how to produce flat topped pressure signals. The experimental condition was for the subjects to produce the syllable string as fast as possible. The subglottal pressure estimates of two vowels from the standard production condition before and after the faster syllables were compared to the subglottal pressure estimates of two vowels from the faster production condition. The first four recordings from subject F4 were excluded from the analysis because of nasal inhalation noted on the flow signal during the task. Syllable rate and lip closed quotient were of concern for the faster task. All subjects increased rate for the faster task. There was an average rate of 1.55 syllables per second for the standard production condition (range: syllables per second) and an average rate of 5.56 syllables per second for the faster condition (range: syllables per second). There was no statistically significant change in lip closed quotient from the standard production condition to the faster production condition, p =.279. The average lip closed quotient for the standard production condition was 39.42% (range: 20.83%-61.14%) and the average lip closed quotient for the faster production condition was 24.48% (range: 0%-42.93%). When the shape was rounded or triangular, the lips often did not close completely during the /p/ occlusion. In these cases (n = 8) the average lip closed quotient was zero because the lips never truly come together as indicated by the flow signal not returning to baseline during the time the lips should be occluded and a reduced pressure signal and reduced time of occlusion visualized. A sign test was conducted to compare the estimates of subglottal pressure during the standard production condition and the faster production condition. There was a statistically significant

64 53 change in the subglottal pressure estimates between the standard production condition and the faster condition, p =.001, with the majority of faster cases showing higher estimates of subglottal pressure than the standard production cases (21 of 26 faster cases across the six subjects had higher estimates of subglottal pressure than the standard production condition). The average difference in pressure between the standard production condition and the faster condition was cm H2O across all subjects. When the sign test was repeated to include only supposed accurate estimates of subglottal pressures, pressures in which equilibration occurred (pressure with a lip closed quotient greater than zero), there was again statistical significance, p =.018, with 15 of 18 cases across the six subjects having higher estimates of subglottal pressure than the standard production condition. The average difference in pressure between the standard production condition and the faster condition for only supposed accurate estimates of subglottal pressure was cm H2O across all subjects. Table 3.4 presents the shapes of oral pressure during the /p/ lip occlusions for the standard production condition and the faster production condition. For the standard production condition and faster production condition the rectangular shape represented 37% and 50% of all the shapes, respectively. The faster production condition had a much higher percentage of rounded shapes (35% for the faster condition vs 4% for the standard) and the standard production condition had a higher percentage of shapes that sloped up to the end portion of the /p/ occlusion (23% for the standard vs 4% for the faster condition). Figure 3.7 presents the frequency of shapes by the two syllable rate regions standard vs faster. While the standard production condition rates present a greater variety of shapes, the faster condition presents more rounded and triangular shapes that cannot be used to estimate subglottal pressure from oral pressure because the vocal tract is never fully occluded (and the flow for these does not go to zero). There

65 54 were 24 syllables that could not be used to accurately estimate subglottal pressure from oral pressure because lip occlusion did not occur (noted by the flow not returning to zero). Of these 24, 10 were rounded, 7 were rounded and had acoustics that continued on across the entire occlusion, 3 were rectangular, 2 were triangular, and 2 were sloped down to the end portion of the /p/ occlusion. Of the 24 syllables in which lip closure did not occur, 12 were between 4.8 and 5.8 syllables per second, 3 between 5.8 and 6.8 syllables per second, and 9 between 6.8 and 7.9 syllables per second. It was hypothesized that estimates of subglottal pressure would be lower for the syllables produced at a faster rate at the same effort level because of the potential inability to have long enough contact for pressure equilibration. The sign test that included only the apparently accurate estimates of subglottal pressure indicated that there was a statically significant change (to higher pressure values) in estimates of subglottal pressure when the rate increased. Further, it was hypothesized that the pressure signal would appear more peaked than the expected nearly rectangular shape that more typically occurs for the standard production condition, and this hypothesis also was supported. When all syllables (accurate and inaccurate syllables) were considered, the faster production condition had more rounded and triangular shaped syllables (more peaked syllables) than the standard production condition (see Table 3.4).

66 55 Table 3.4. Shape Characteristics of Three Faster and Six Standard Production Syllables for Six Subjects Standard Production Condition Faster Production Condition Shape n % N % Rectangular (36) 50 (46) Sloped up to the end of lip occlusion Sloped down to the end of lip occlusion (3) 6 (4) Pressure dip during the occlusion Pressure increase during the occlusion Wavy flat portion Pressure highest at end portion of /p/ occlusion Pressure highest at initial portion of /p/ occlusion Rounded (10) 35 (13) Triangular (2) 5 (3) Pressure step down Pressure step up Occlusions containing multiple shape (3) 13 (4) characteristics Note. Total number of syllables in standard production condition = 156, total number of syllables in the faster production condition = 78. % is percentage occurrence of each shape relative to the total number of shapes (faster production condition n = 88, standard production condition n = 162). Occlusions that contained shape characteristics that could be categorized in more than one way are counted for both shapes. Thus, the total number of shapes in the table is greater than the total number of syllables because occlusions containing multiple shape characteristics are counted for each characteristic in the table. The number in parentheses represents the shape count (n) and the percentage (%) of the pressure shapes that provide what are thought to be accurate estimates of subglottal pressure during a faster rate. See Table 3.1 for definitions of the patterns mentioned in this table.

67 56 Frequency of Shapes by Syllable Rate Count SPC Faster Rate (syllables per second) Rectangular Pressure dip Rounded Acoustics continue through occlusion Sloped to the end portion of /p/ occlusion Pressure highest end portion of /p/ occlusion Triangular Figure 3.7. Frequency of Oral Pressure Shape Characteristics by Syllable Rate. This figure presents the frequency of shapes for varying rate ranges with the range of 1.2 to 2.0 syllables per second representing the standard production condition (SPC) and the range of 2.8 to 7.9 syllables per second representing the faster condition. Inherently, a change in rate should not change the subglottal pressure if the system is equilibrating adequately for a constant lung pressure. However, an increase in rate tended to result in an increase in estimates of subglottal pressure from oral pressure relative to the standard production condition. This seems counterintuitive if one were to hypothesize that when rate increases the lips may not come together completely and the pressure estimates would be lower. Reasons why the pressure estimates would be higher are considered below. The first consideration when looking at increasing rate is whether or not the vocal tract became fully occluded. The lips must move from a separated position to produce the vowel to a closed position to produce the consonant, while the vocal folds must move from an adducted position for the vowel to a separated position for the consonant. The lips must be fully together for the oral pressure to equal the subglottal pressure (Netsell & Hixon, 1978). If the lips do not

68 57 close, the estimates of subglottal pressure should be reduced because a leak causes a decrease in pressure (Figure 3.8) if the lung pressure remained constant. To maintain lip closure, the contact pressure created by the lips must be greater than or equal to the intraoral pressure built up behind the lips (Hinton & Luschei, 1992). Figure 3.8. Oral Airflow and Oral Pressure Signals for Fast Syllables. This figure presents the flow and pressure signals (upper and lower traces) from a male subject (M4) using a rate of 7.11 syllables per second (average lip closed quotient of 10% for the syllables marked). A horizontal line was placed across the baseline (zero flow) of the flow signal. The flow and pressure signals suggest that the attempted syllable rate was so fast that the lips were not closed long enough for the flow to return to baseline, the phonation to stop, and the system to equilibrate air pressure. It would be inappropriate and inaccurate to use this recording to estimate subglottal pressure during the vowel. However, an increase in the estimates of subglottal pressure during the leak was often seen in this study. More effort, often perceived as a change in loudness, is thought to be caused by an increase in subglottal pressure (e.g., Gauffin & Sundberg, 1989; Hixon, Weismer, & Hoit, 2008; Kent, 1997; Raphael, Borden, & Harris, 2003). During the current study loudness was not measured. Intensity values were extracted from Praat from the microphone signal. A sign test indicated that there was no difference in intensity between the standard production conditions and the faster rate conditions across all subjects, p =.423. As a side note, increase in subglottal pressure has often been related to (and the indirect cause of) an increase in pitch (e.g., Broad, 1973; Raphael et al., 2003; Titze, 1989). The average

69 58 pitch across all subjects (male and female) for the standard production condition was 198 Hz and the average pitch across all subjects for the faster rate condition was 203 Hz (about a 5 Hz difference). This difference could be expected to be caused by a 1 to 2 cm H2O difference in lung pressure, as Titze (1989) estimated that there is a 2-6 Hz increase per 1 cm H2O increase in pressure. The accurate faster conditions were on average 1.5 cm H2O greater than the standard production condition estimates of subglottal pressure. All subjects were instructed to use a constant loudness across the tasks. The researchers did not note any changes in loudness during the recording process. More energy in higher frequencies, or a brighter voice, is also thought to be a consequence of subglottal pressure increase (Gauffin & Sundberg, 1989). There were no noted changes in brightness during the recordings (although any spectral changes were not studied in this research). PART 3: Initial Voicing In the Part 3 recordings, each subject was instructed to produce all syllables in the standard production condition so that they had flat tops with the first and last set of syllables as peep. The middle experimental set of syllables was a sequence of beep syllables, also with the request to be produced smoothly. The peep syllables had an average rate of 1.59 syllables per second (range: 1.17 to 2.17 syllables per second) and the beep syllables had an average rate of 1.61 syllables per second (range: 1.18 to 2.17 syllables per second). The average lip closed quotient of the peep syllables was 36% (range: 13% to 59%) and the average lip closed quotient of the beep syllables was 37% (range: 7% to 64%). A sign test was conducted to compare the estimates of subglottal pressure for the voiced initial syllables and the unvoiced initial syllables. The sign test indicated that there was no

70 59 difference in subglottal pressure estimates during the vowel for the voiced and unvoiced initial consonants, p =.292. The average difference in estimates of subglottal pressure between the peep and the beep syllables was cm H2O. The initial voiced syllable and the initial unvoiced syllable were mostly rectangular shaped, 54% and 44%, respectively. The voiced and unvoiced syllables were also often sloped up to the end portion of the /p/ occlusion (15% and 19%, respectively) and often included a pressure dip during the /p/ occlusion (9% and 12%, respectively). Table 3.5 presents the breakdown of all shapes found in the voiced and unvoiced initial production task. The flow signal indicated lip closure for all cases (there was zero flow during lip occlusions). In addition, the lips were closed long enough for pressure to build up for all /p/ and /b/ syllables. It was hypothesized that beep syllables would give accurate estimates of subglottal pressure because aspiration is reduced. The beep syllables gave rectangular shaped /b/ lip occlusion pressures for 10% more cases than the peep syllables did. The beep syllables had fewer oral pressure signals that were sloped upwards towards the release (where aspiration occurs) or the end portion of /b/ occlusion. The beep syllable also had fewer oral pressure signals with the highest pressure at the end of the occlusion where aspiration occurs. Overall, the beep syllables gave similar estimates of subglottal pressure as the peep syllables did, and had more shapes that were consistent with increased accuracy of subglottal pressure estimates, suggesting that beep sequences may be just as useful, or more so, than peep sequences for studies of estimating subglottal pressure, especially in cases where using less air would be a benefit (as was the case in the study of whisper by Konnai, 2012).

71 60 Table 3.5. Shape Characteristics of Three Voiced Initial Consonants and Six Standard Production Syllables with Unvoiced Initial Consonants for Six Subjects Unvoiced Initial Syllable /p/ Voiced Initial Syllable /b/ Shape n % n % Rectangular Sloped up to the end of lip occlusion Sloped down to the end of lip occlusion Pressure dip during the occlusion Pressure increase during the occlusion Wavy flat portion Pressure highest at end portion of /p/ or /b/ occlusion Pressure highest at initial portion of /p/ or /b/ occlusion Rounded Triangular Pressure step down Pressure step up Occlusions containing multiple shape characteristics Note. Total number of syllables in standard production condition = 180, total number of syllables voiced initial consonant = 90. % is percentage occurrence of each shape of the total number of shapes (initial voiced consonant n = 94, standard production condition with initial unvoiced consonant n = 181). Occlusions that contained shape characteristics that could be categorized in more than one way are counted for both shapes. Thus, the total number of shapes in the table is greater than the total number of syllables because occlusions containing multiple shape characteristics are counted for each characteristic in the table. See Table 3.1 for definitions of the patterns mentioned in this table. Over the years, researchers and clinicians have been concerned about using a voiced stop consonant /b/ instead of a voiceless stop consonant /p/ to obtain estimates of subglottal pressure from the oral pressure (e.g., Plexico, Sandage, & Faver, 2011). The unvoiced consonant /p/ is used because the glottis is open during production of /p/, allowing pressure to equilibrate across the vocal tract. A /b/ may be used to reduce the influence of aspiration on the oral signals at the initiation of the /b/ following the duration of the lip occlusion.

72 61 However, Shipp (1973) was also concerned with the lip release in both /p/ and /b/. As /p/ is voiceless, the glottis is open when the /p/ is released (voiceless stop consonant) so the lag between the lip opening and the significant drop in oral pressure is suggested to be because the already large vocal tract volume is less impacted by the introduction of a small lip leak prior to the burst (Shipp, 1973). In contrast to /p/, a /b/ consonant presents with more rapid reduction in oral pressure when the lips are separated (Shipp, 1973). Concern has also been given to the impact of aspiration from the /p/ on the estimates of subglottal pressure. Kitzing and Löfqvist (1975) suggest that aspiration mainly impacts where in the vowel you are estimating subglottal pressure. Namely, they suggest that the influence of aspiration causes the vocal folds to begin vibration for the vowel later because the vocal folds must adduct to begin vibration from the voiceless consonant. For this case, they suggest estimating subglottal pressure from the middle of the vowel. For an initial voiced consonant, the voicing of the vowel begins almost immediately after the lips are open, indicating the subglottal pressure during the vowel can be estimated accurately sooner (Kitzing & Löfqvist, 1975). Kitajima and Fujita (1990) further note that if one is attempting to measure flow resistance, the flow at the point just when the pressure returns to zero during the vowel is not an accurate place to measure flow rate as it is influenced by aspiration. In the current study, there was no statistically significant difference between estimates of subglottal pressure from oral pressure between the voiced and voiceless plosives. Both tended to show the most rectangular shaped occlusions and always had flow signals that indicated full occlusion of the vocal tract. The flow signal should be monitored for a large change in lung volume during aspiration (Konnai, 2012) that indicates the pressure may be changing during the vowel.

73 62 PART 4: Misarticulations For Part 4, the subject was instructed to produce all syllables in the standard production condition with intended flat tops for the first and last set of syllables, with the middle set of syllables in the breath group being produced with a bilabial fricative, thus mimicking a lip leak because of a bilabial misarticulation. One recording from M1 was excluded from analysis because the subject inhaled between the experimental condition and the second standard production condition. F5 was not included in this analysis because analysis of this subject s recordings has not yet been completed. The standard production condition syllables had an average rate of 1.61 syllables per second (range: 1.13 to 2.29 syllables per second) and the misarticulated syllables also had an average rate of 1.61 syllables per second (range: 1.18 to 2.32 syllables per second). The average lip closed quotient for the standard production condition syllables was 34% (range: 11% to 56%) and the average lip closed quotient of the misarticulated syllables was 37% (range: 0% to 41%). A sign test was conducted to compare the estimates of subglottal pressure for the standard production condition and the lip leak condition. The sign test indicated that there was a statistically significant difference between the lip leak condition and the standard production condition, p =.002, indicating that the estimates of subglottal pressure during the adjacent vowel would be too low during the experimental task of the lip leak. The average difference in estimates of subglottal pressure between the standard production condition and the misarticulated syllables was 1.1 cm H2O. Of the 25 tokens from the lip leak task, 8 presented with accurate estimates of subglottal pressures. That is, there were 8 sets of the experimental lip-leak tokens across all subjects where the subjects did not produce the misarticulation task correctly, and

74 63 instead produced full lip closure. When a sign test was repeated with the tokens without a lip leak removed, the test again indicated that there was a statistically significant difference between the lip leak condition and the standard production condition, p <.001. The average difference in estimates of subglottal pressure increased from 1.1 cm H2O to 1.5 cm H2O after the incorrect experimental tasks were removed. Table 3.6 shows the breakdown of shapes for the standard production condition and lip leak syllables. The majority of the standard production condition syllables were rectangular (47%). Many standard production condition syllables were sloped up to the end portion of the /p/ occlusion (17%), had a pressure dip during the occlusion (13%), or had higher pressure on the initial portion of the /p/ occlusion (12%). The majority of the lip leak syllables were rounded (47%); however, many were thought to provide inaccurate estimates of subglottal pressure as indicated by the flow not returning to zero flow baseline during the occlusion. When the lip leak oral pressure shapes that were thought to provide accurate estimates of subglottal pressure were removed, it is clear that the majority of the syllables were rounded (63%). It was hypothesized that when the misarticulation, or lip leak, is introduced, the estimates of subglottal pressure would decrease due to a lack of equalization of air pressure from the lungs to the oral cavity. 68% of the syllables from the misarticulated condition were considered to be inaccurate in that regard due to a lack of equalization of air pressure noted by the flow not returning to baseline during the occlusion. When all the pressures (those thought to provide accurate estimates and those thought to provide inaccurate estimates of subglottal pressure) were considered, the misarticulated condition did present with lower estimates of subglottal pressure than the standard production condition. The supposedly accurate conditions had no flow during the occlusion, indicating that there was not a true leak, thus there was no statistically significant

75 64 difference between estimates of subglottal pressure. Figure 3.9 presents the pressure change from the standard production condition to the misarticulation condition for all subjects. The figure includes data for all cases with a lip leak. All subjects except F4 show a decrease in pressure from the standard production condition to the misarticulation condition. Table 3.6 Shape Characteristics of Three Initial Consonants with a Lip Leak and Six Standard Production Syllables for Five Subjects Standard Production Lip Leak Condition Shape n % n % Rectangular (1) 8 (2) Sloped up to the end of lip occlusion (4) 8 (7) Sloped down to the end of lip occlusion (2) 10 (4) Pressure dip during the occlusion (1) 5 (2) Pressure increase during the occlusion (0) 1 (0) Wavy flat portion Pressure highest at end portion of /p/ occlusion (1) 5 (2) Pressure highest at initial portion of /p/ occlusion (1) 3 (2) Rounded (34) 47 (63) Triangular (10) 13 (19) Pressure step down Pressure step up Occlusions containing multiple shape characteristics Note. Total number of syllables in standard production condition = 150, total number of syllables voiced initial consonant = 74. % is percentage occurrence of each shape of the total number of shapes (initial lip leak consonant n = 74, standard production condition n = 158). Occlusions that contained shape characteristics that could be categorized in more than one way are counted for both shapes. Thus, the total number of shapes in the table is greater than the total number of syllables because occlusions containing multiple shape characteristics are counted for each characteristic in the table. The number in parenthesis represents the shape count (n) and the percentage (%) of the pressure shapes after those that provide accurate estimates of subglottal pressure during a lip leak were removed. See Table 3.1 for definitions of the patterns mentioned in this table.

76 65 Figure 3.9. Pressure Change from Standard Production Condition to Lip Leak/Misarticulation. The average estimated subglottal pressure for the standard production condition and the misarticulation condition are presented in the figure for each subject. All subjects except F4 showed a decreased in pressure from the standard production condition to the misarticulation condition. The airway must be completely occluded during a consonant production to allow for equilibration within the vocal tract. When any type of leak is introduced into the system, the estimates of subglottal pressure from oral pressure will underestimate the actual subglottal pressure during the adjacent vowel because the same amount of pressure that built up to drive the vocal folds during the vowel did not build up behind the lips. During a lip leak condition (/ i/) pressure may be lost during the occlusion. In Figure 3.10, the first syllable and the last /p/ occlusion shown are standard production condition /p:i:/ syllables produced with full lip closure. For the remainder of the syllables, the flow not returning to baseline during the period of the consonant suggests that airflow is moving between the lips. Any estimates of subglottal pressure from oral pressure signals including a lip leak would

77 66 underestimate the subglottal pressure (as seen when comparing the standard production condition syllables and the lip leak syllables in Figure 3.10). Figure Multi-Signal Example of Lip Leak. Microphone, flow, pressure, and EGG (from top to bottom) signals for several syllables during a lip leak condition (M4). The horizontal line indicates when flow returns to baseline (where full occlusion of the vocal tract occurs). In this case the lips do not appear to be closed and thus do not allow for accurate estimates of subglottal pressure. Estimates of subglottal pressure from this syllable will likely undershoot the actual subglottal pressure. PART 5: Velar Leak Part 5 required subjects to produce the initial consonant of the experimental task with a substantial velar leak. Subjects produced the initial consonant as /m/ in most cases. F5 was not included in this analysis because analysis of this subject s recordings was not completed. To determine the oral air pressure during the velar leak consonant, the average of all pressure values during the consonant were averaged. It is noted that during the /m/, the oral cavity has both a mean air pressure as well as significant acoustic pressure; the overall average reveals the mean

78 67 pressure. The standard production condition syllables had an average rate of 1.64 syllables per second (range: 1.15 to 2.27 syllables per second) and the velar leak syllables had an average rate of 1.69 syllables per second (range: 1.27 to 2.32 syllables per second). The average lip closed quotient of the standard production condition syllables was 30% (range: 9% to 60%) and the average lip closed quotient of the velar leak syllables was 37% (range: 12% to 62%). A sign test indicated that there was a statistically significant difference in estimates of subglottal pressure between the standard production condition and the velar leak task, p <.001, with all cases presenting with lower pressures for the velar leak task (mean difference: 7.87 cm H2O, range: 3.89 to cm H2O). During the velar leak condition, airflow never returned to baseline (Figure 3.11). This suggests that the pressure never equilibrated because there was always air moving throughout the vocal tract. As the pressure did not equilibrate in the vocal tract, none of the estimates of subglottal pressure from oral pressure are considered accurate relative to the subglottal pressure for the adjacent vowels.

79 68 Figure Multi-Signal Example of Velar Leak. Microphone (top signal), air flow (2 nd signal from the top), oral pressure (3 rd signal from the top) and EGG (bottom signal) for a male subject (M2) producing four syllables in the standard production condition, four syllables with an initial velar leak (/m/), and then four syllables in the standard production condition. Notice during the standard production condition syllables the airflow is at baseline during the /p/ lip occlusion (denoted by an arrow). During the velar leak condition, the airflow never returns to baseline, indicating that the pressure does not equilibrate across the vocal tract and the oral pressure during the velar leak consonant is not an accurate estimate of subglottal pressure during the vowel. It was hypothesized that in a velar leak condition the air escape through the nose would prevent full pressure equilibration resulting in reduced estimates of subglottal pressure. All velar leak syllables were lower than standard production condition syllables (Figure 3.13). The flow during the velar leak consonant never returned to baseline. The experimental condition presented an extreme velar leak with an extreme difference in pressure between the standard production condition and the experimental condition.

80 69 Figure Estimated Subglottal Pressure Change from Standard Production Condition to Velar Leak Condition. The average estimated subglottal pressure for the standard production condition and the velar leak condition are presented in the figure for each subject. All subjects showed a substantial decreased in pressure from the standard production condition to the velar leak condition. The velar leak in Part 5 was an extreme voiced velar leak (/m/). The tasks did not include a voiceless lip occlusion with velopharyngeal port opening. Velopharyngeal port opening would have produced large airflow through the nose and a significant decrease in pressure, as is understood from the craniofacial literature (e.g., Guyette, Sanchez & Smith, 2000). Here voicing was continued with the /m/ production during lip occlusion. Replication with a voiceless /p/ occlusion accompanied by a velar leak should be used in future research to determine the impact on the oral pressure and flow. As found in the current study, Thompson and Hixon (1978a) found that during a nasalized consonant, the flow was not at baseline (Figure 3.13). The velar leak that results in lowered oral pressures has been emphasized as a significant methodological error by Fisher and Swank (1997).

81 70 Figure Average Oral Airflow and Oral Pressure Signals for Standard Production Condition and Velar Leak Condition. This figure shows the flow and intraoral pressure signals for a velar leak condition for subject M4. The flow is never at baseline during the nasal consonant. Because the nasal consonant is voiced, the flow and intraoral pressure both show modulations due to the influence of acoustic pressure. PART 6: One Syllable versus Two Syllables Recently, Rothenberg (2013) has requested that researchers use more natural speech strings to estimate subglottal pressure from oral pressure. In the current study, the two syllable utterance peeper was used to create a more linguistic sample from which to estimate subglottal pressure. Peeper was chosen because the /i/ used is in a similar position as in the standard production condition, that is, it is surrounded by the voiceless stop plosive /p/. The subjects were instructed to use the same stress on the /pi/ as they used for the /p:i:p/ in the standard production condition. This would make the /pi/ syllable slightly more stressed than the /p / syllable. For Part 6, the subject was asked to produce the first and last set of syllables as standard production condition syllables. The middle syllables were produced as the two syllable utterance /pip /. The rate was to be around 3.0 syllables per second so that both syllables were produced in the same amount of time as the one syllable from the standard production condition. The average rate of the standard production condition was 1.61 syllables per second (range: 1.18 to 2.31 syllables per second) and the average rate of the two syllable production was 3.33 syllables per second (range: 2.57 to 4.71 syllables per second). The average lip closed quotient of the standard

82 71 production condition was 33% (range: 12% to 62%). The lip closed quotient is not an appropriate measure for the two syllables in the /pip / production because the second syllable does not end in a stop consonant to close the syllable. The average amount of time the lips were closed was measured as milliseconds for the first /p/ in the /pip/ syllable (range: ms to ms) and average time the lips were closed for the /p/ in the /p / syllable was ms (range: ms to ms). F5 was not included in this analysis because analysis of this subject s recordings was not completed. The subglottal pressure of the experimental task was estimated for the /i/ vowel (taken as the average of the average of all oral pressures during the lip occlusions before and after the vowel) to make it comparable to the estimate of subglottal pressure from the standard production condition. A sign test was conducted to compare the estimates of subglottal pressure for the one syllable standard production condition and the first syllable of the two syllable condition. The sign test indicated that there was no significant difference in subglottal pressure estimates during the vowel for the two conditions, p =.212. The average difference between the estimate of subglottal pressure for the standard production condition and the two syllable production was cm H2O. As the first syllable was stressed and the second unstressed, the shapes in Table 3.7 are broken down to understand the differences in shaping of the oral pressure during the /p/ occlusion for both the unstressed and stressed syllable. For all syllables, the rectangular shape was the most prevalent. A shape sloped up to the end portion of the /p/ lip occlusion was common for the /pi/ syllable. This is a higher pressure just before the stressed /i/ vowel. Similarly, a slope down to the end portion of the /p/ occlusion was common for the /p / syllable, again because the pressure was higher just after the stressed /i/ vowel.

83 72 Table 3.7. Shape Characteristics of Three Two Syllable Productions /pip / and Six Standard Production Syllables for Five Subjects Standard Production Condition Two Syllable Condition /pi/ Two Syllable Condition /p / Shape N % N % n % Rectangular Sloped up to the end of lip occlusion Sloped down to the end of lip occlusion Pressure dip during the occlusion Pressure increase during the occlusion Wavy flat portion Pressure highest at end portion of /p/ occlusion Pressure highest at initial portion of /p/ occlusion Rounded Triangular Pressure step down Pressure step up Occlusions containing multiple shape characteristics Note. Total number of syllables in standard production condition = 150, total number of twosyllable productions in the experimental condition = 100. % is percentage occurrence of each shape of the total number of shapes (two syllable condition n = 100, standard production condition n = 152). Occlusions that contained shape characteristics that could be categorized in more than one way are counted for both shapes. Thus, the total number of shapes in the table is greater than the total number of syllables because occlusions containing multiple shape characteristics are counted for each characteristic in the table. See Table 3.1 for definitions of the patterns mentioned in this table. It was hypothesized that if there were sufficient rise time for the oral pressure during the lip occlusion, the occlusion pressures from the two syllable production should give similar estimates of subglottal pressure to the one syllable standard production condition estimates of subglottal pressure, but perhaps with some variation due to the different vowel stresses. The lip closed quotients for both syllables of the experimental condition were similar to the lip closed quotients for the standard production condition, indicating that there was enough time for the

84 73 vocal tract to equilibrate during the production of both syllables. This, along with non-significant results from the sign test, indicate that the estimate of subglottal pressure for the /i/ vowel appear to be accurate for this two-syllable production. Pilot work suggested that the best approximation of the subglottal pressure during the stressed vowel would be an average between the pressure at the end of occlusion before the stressed vowel and the pressure at the beginning of occlusion after the stressed vowel. The majority of pressure occlusions from the pilot work were sloped up or down towards the stressed vowel. The majority of pressure occlusions in the study were rectangular with 62% rectangular shaped occlusions before the stressed vowel and 52% rectangular shaped occlusions after the stressed vowel. As the shapes were not sloped, the suggestion to take the last moment of occlusion before the stressed vowel and the first moment of occlusion after the stressed vowel did not apply and was thus not used in the current study. Netsell (1973) reported that the oral pressure signal during the occlusion may be sloped upward to the more stressed vowel. In the current study, after rectangular shaping, the first syllable had the highest percentage of syllables sloped up towards the end of the /p/ occlusion or towards the stressed vowel (28%) and the second syllable had the highest percentage of syllables sloped (upwards) towards the beginning (to the left) of the /p/ occlusion or towards the stressed vowel (18%), supporting the statement by Netsell (1973). The data regarding the changes in subglottal pressure that result from stressed syllables show mixed results. Liberman (1967), as cited by Gay (1978), indicated that there were differences in subglottal pressure between stressed and unstressed syllables and that these differences in subglottal pressure lead to changes in intensity and fundamental frequency. Karlsson (1988) found little difference in subglottal pressure across speakers in a study of

85 74 speakers with different categorized speech types and different stress conditions. Subglottal pressure was not a main focus of that study, and the results are not clear about how subglottal pressure was compared to the other variables. Ladefoged (1963) found that an increase in stress was always accompanied by an increase in subglottal pressure. Subtelny, Worth, and Sakuda (1966) looked only at intraoral pressure and found that for stressed vowels, the intraoral pressure was always higher with a longer period of pressure plateau. In the current study, the consonant preceding the stressed vowel had on average a slightly higher lip closed quotient (37%) than the unstressed vowel (34%). There was also no statistically significant difference in estimates of subglottal pressure between the unstressed single syllable and the stressed initial syllable of a two syllable production. The current study suggests that using a word, like Rothenberg (2013) suggests, may be an appropriate method of estimating subglottal pressure. Anecdotally, the subjects in the current study needed less training to produce the two syllable production with relatively flat tops. This may be due to the two syllable task being the last task of the experiment. Further research should be conducted to determine (a) if words with linguistic stress are giving accurate estimates of subglottal pressure in the oral cavity when compared to actual measures of tracheal pressure, and (b) if using words provides easier as well as accurate estimates of subglottal pressure than using smoothly produced syllable strings. Comparison of Estimates of Subglottal Pressure across Experimental Conditions In this section, the results for each of the 6 subjects of this report will be discussed relative to a comparison between the standard and experimental conditions. It is noted that instead of differences between the oral pressures for the standard and experimental conditions, the actual pressures will be shown in figures here. For example, subject M1 s data are shown in

86 75 Figure In this figure box and whisker plots show the calculated pressures for the standard condition tokens as well as for the tokens for each of the experimental conditions. When examining subject M1 individually, there was a great range of estimates of subglottal pressure from oral pressure taken from the standard production condition (approximately 7.55 cm H2O to cm H2O), as shown in Figure This suggests that the subject used varying amounts of effort or loudness while producing the standard across the experiments, even after being instructed to produce the standard production condition with constant effort (e.g., Gauffin & Sundberg, 1989; Hixon, Weismer, & Hoit, 2008; Kent, 1997; Raphael, Borden, & Harris, 2003). When subject M1 increased rate, there was less variability in the range of the estimates of subglottal pressure (range: cm H2O to cm H2O) and all values fell above the 75th percentile of the standard condition data (Figure 3.14). Thus, increased syllable rate tended to increase the oral pressures for this subject. For Subject M1, there appears to be very little difference in estimates of subglottal pressure for the estimates in the presence of a lip leak and the voiced initial consonant. For both conditions, approximately 75% of the estimates fell below the median estimate of the standard production condition, meaning that most of the pressures for lip leak and initial /b/ tokens were less than for the standard. The extreme velar leak for /m/ shows a marked decrease in estimates of subglottal pressure. The two syllable production of /pip / has a smaller range of estimates of subglottal pressure (12.13 cm H2O to 15.1 cm H2O) and a median estimate that is.83 cm H2O higher than the standard production condition, and thus the estimates of subglottal pressure made from the two syllable production are the most similar to the standard production condition for subject M1.

87 76 Figure Box and Whisker Plot for all Condition for Subject M1. Box and whisker plot of the estimates of subglottal pressure from oral pressure for subject M1 across all conditions. The whiskers represent the minimum and maximum subglottal pressure estimates. Subject F2 had a greatly reduced range and median values of estimated subglottal pressure for the standard production condition (5.27 cm H2O to 8.54 cm H2O) than subject M1 (Figure 3.15). For the faster condition, all of the estimates of subglottal pressure again fell above the 75 th percentile of the estimates from her standard production condition. For the initial voiced syllable (/bip/) the median estimates of subglottal pressure are nearly identical to the median estimate of subglottal pressure for the standard production condition (6.56 cm H2O and 6.64 cm H2O, respectively).there is also a very similar, although narrower range of estimated subglottal pressure for the initial voiced syllable compare to the standard production condition (5.88 cm H2O to 7.84 cm H2O). Of all the conditions expected to give similar estimates of subglottal pressure to the standard condition (faster, initial voiced, and two syllable conditions), the voiced initial syllable presents the closest estimate. In the lip leak condition, all of the pressure estimates

88 77 fall in the bottom 25% of the estimates from the standard production condition. While the velar leak shows a profound decrease in estimates of pressure, subject F2 had the highest estimates of subglottal pressure from oral pressure from the lip leak condition, indicating that from the standard to the lip leak condition, subject F2 had the least amount of pressure decrease. For the two-syllable production, subject F2 had a similar median pressure estimate to the standard production condition and the initial voiced condition (6.13 cm H2O). Like the initial voiced syllable, the two syllable production provides reasonable estimates of subglottal pressure that are similar to the estimates of the standard condition. Figure Box and Whisker Plot for all Condition for Subject F2. Box and whisker plot of the estimates of subglottal pressure from oral pressure for subject F2 across all condition. The whiskers represent the minimum and maximum subglottal pressure estimates. Subject M2 had a relatively narrow range, approximately 3 cm H2O for the pressure estimates for the standard production condition (Figure 3.16). When subject M2 increased his rate, estimates of subglottal pressure dropped below the 50 th percentile of the estimates of

89 78 subglottal pressure made from the standard production condition. The initial voiced consonant condition represented the narrowest range of estimates of subglottal pressure (6.05 cm H2O to 6.73 cm H2O). All estimates for the initial voiced consonant condition surround the median estimate of the standard production condition. For subject M2, when a lip leak was introduced, all values fell below the minimum estimate of subglottal pressure from oral pressure from the standard production condition. As subject M2 produced some syllables without a lip leak, only three pressure values were used to create the box and whisker plot for the lip leak condition. As expected, the extreme velar leak presented a pressure decrease. The two syllable production has a similar (slightly lower) but narrower range of estimates of subglottal pressure than the standard production condition. For subject M2, the faster, initial voiced syllable, and two syllable production presented the most similar estimates of subglottal pressure to the standard production condition. Relative to the other subjects, subject M2 showed the most stable estimate of subglottal pressure across the standard production condition, the faster condition, the initial voiced consonant condition, and the two syllable condition. This subject also showed a narrow range of estimates of subglottal pressure for all conditions, suggesting that this subject was well trained and produced the most reliable estimates of pressure.

90 79 Figure Box and Whisker Plot for all Condition for Subject M2. Box and whisker plot of the estimates of subglottal pressure from oral pressure for subject M2 across all condition. The whiskers represent the minimum and maximum subglottal pressure estimates. Subject F4 had an approximately 4 cm H2O range of estimates of subglottal pressure for the standard production condition (Figure 3.17). No quartiles could be calculated for the faster condition because only two estimates of subglottal pressure (11.19 cm H2O and cmh2o) could be made due to nasal inhalations on the other recordings. These pressure estimates are both higher than all estimates of pressure from the standard production condition. The narrow range of estimates from the initial voiced syllables all fall within the upper 50% of the estimates from the standard production condition. The estimates from the lip leak condition for subject F4 represent the greatest range of lip leak pressure estimates (6.46 cm H2O to cm H2O). There were only four pressure estimates for the lip leak condition as the subject produce several syllables without a lip leak. As for all subjects, the velar leak condition presented with a decrease in estimates of subglottal pressure. The estimates of subglottal pressure for the two syllable

91 80 production has a narrow range that is just around the median of the standard production condition (7.54 cm H2O to 8.59 cm H2O). Subject F4 was the most difficult subject to train. This would explain the 4 cm H2O range of estimates of subglottal pressure for the standard production condition and the lack of recordings that could be analyzed for the faster condition and the lip leak condition. Despite being difficult to train, consistent estimates of subglottal pressure were able to be obtained from the initial voiced consonant and the two syllable production. These estimates also appear to be reasonable based on how similar they are to the standard production condition. Figure Box and Whisker Plot for all Condition for Subject F4. Box and whisker plot of the estimates of subglottal pressure from oral pressure for subject F4 across all condition. The data points are presented for the faster production condition because subject F4 presented only one faster production recording that did not include a nasal inhalation. The whiskers represent the minimum and maximum subglottal pressure estimates. Similar to M1, subject M4 presented with a wide range of standard production condition pressure estimates (4.84 cm H2O to cm H2O) (Figure 3.18). For the faster condition,

92 81 nearly all of subject M4 s estimates of subglottal pressure fall above the 75 th percentile of the pressure estimates from the standard production condition. For the voiced initial syllable condition, the estimates of subglottal pressure had a very narrow range (9.34 cm H2O to 9.88 cm H2O). These pressures also were above the 75 th percentile of the pressure estimates from the standard condition. The lip leak condition was the most variable of all the subjects for subject M4 with over a 5 cm H2O range. The majority of the estimates for the lip leak condition fall below the estimates from the standard condition. Again, the velar leak demonstrated a large decrease in estimates of pressure. The two-syllable production presented with a narrow range of estimates of pressure that were similar to the estimates from the standard production condition (9.12 cm H2O to 10 cm H2O). For subject M4, the most similar estimates of subglottal pressure to standard are from the initial voiced condition and the two-syllable condition. Figure Box and Whisker Plot for all Condition for Subject M4. Box and whisker plot of the estimates of subglottal pressure from oral pressure for subject M4 across all condition. The whiskers represent the minimum and maximum subglottal pressure estimates.

93 82 Subject F5 presented an approximately 2 cm H2O range in estimates of subglottal pressure in the standard production condition (Figure 3.19). Both the faster condition and the initial voiced condition have pressure estimates that fall just around the median estimates of pressure of the standard production condition. Subject F5 was the most consistent of all subject on all three conditions. Figure Box and Whisker Plot for Three Condition for Subject F5. Box and whisker plot of the estimates of subglottal pressure from oral pressure for subject F5 for the standard production condition, the faster condition and the initial voicing condition. Data analysis is in progress for the other conditions. The whiskers represent the minimum and maximum subglottal pressure estimates. When looking across the subjects, a basic observation is that great care should be taken to develop a constant standard estimate of subglottal pressure. This will ensure that changes seen after treatment or worsening of a voice problem reflect the physiological changes and not an inconsistent methodology. The introduction of a leak, either at the lips or at the velum, result in a reduction of estimates of subglottal pressure from the standard. Any estimates of subglottal

94 83 pressure from oral pressure made in the presence of a leak should be considered inaccurate and not be used to make decisions. For two subjects (M2 and F5) the estimates of subglottal pressure from the faster condition appear to be reasonable estimates of subglottal pressure. These subjects used an average rate of 5.65 syllables per second and 5.49 syllables per second, respectively for the faster condition. These were not the slowest rates used (subject M1 used a faster rate of 3.02 syllables per second and subject F4 used a faster rate of 5.7 syllables per second). However, subjects M1 and F4 were difficult to train and may have had more inconsistent pressure estimates at their faster rates, which were similar to the faster rates of subject M2 and F5. The other two subjects with higher estimates of subglottal pressure than the standard for the faster condition had syllable rates greater than 6 syllables per second. It appears that, as previously stated, the faster condition may provide accurate estimates of subglottal pressure as long as the rate does not increase so much that the lips cannot properly close. It also appears that the subject must be able to consistently produce the standard production condition to be able to get similar estimates from the faster condition. In lieu of the standard condition, it appears reasonable to use the initial voiced syllable or the two syllable production to estimates subglottal pressure. Five of the six subjects gave similar estimates of subglottal pressure to the standard condition from the voiced initial syllable (subjects F2, M2, F4, M4, and F5). The initial voiced syllable for subject M1 had a similar median to the standard production condition, but the range of pressure estimates was too great to trust the estimate. All of the subjects analyzed had similar pressure estimates to the standard for the two syllable production. Subject F5 was not analyzed for this condition. The accuracy of the

95 84 estimates of subglottal pressure from the initial voiced syllable and the two syllable production should be verified by actual measures of subglottal pressure. Other Conditions to Consider Lip closed time. In addition to the flow returning to zero during the /p/ occlusion to indicate that equilibration of the vocal tract has begun, the lips need to be closed long enough to allow for full equilibration. For the fastest condition (Part 2), the shortest duration of lip closed time that allowed for accurate estimates of subglottal pressure was milliseconds. Subject M4 was able to produce the shortest lip closed times overall. This subject tended to produce more rectangular oral pressure signals when the lip closed time was between 20 ms and 30 ms. In Figure 3.20, the oral pressure profiles (bottom) appear to not plateau long enough to achieve equilibration in the vocal tract except for the fifth syllables. However, when the flow is examined, the flow appears to return to zero for all syllables shown. Although flow going to zero is a prerequisite for pressure equilibration, it does not mean that the vocal tract is equilibrated fully. The flow returning to zero indicates that vocal tract equilibration has begun. The lips need to be closed long enough to allow full equilibration of the vocal tract and allow the oral pressure during the consonant to equal subglottal pressure during the vowel. In the figure, the estimates of subglottal pressure for the narrower syllables would be too low and appear to have too short of an occlusion time for equilibration. The step up patterns of the second, fifth, and sixth pressure profile suggests vocal tract volume changes during the lip occlusion as might arise from a rising jaw throughout most of the profile.

96 85 Figure Multi-Signal Example of Reduced Lip Closure Duration as Estimated from the Oral Pressure Signal. This figure shows the microphone, flow, and pressure (from top to bottom) from a standard production condition recording from subject M1. The pressure of the middle syllables is triangular shaped and lower than surrounding pressures. It does not appear to provide accurate estimates of subglottal pressure despite the observation that lip closure is complete (the flow has gone to zero during the lip occlusion). However, near the time of 1.9 s, there is voicing on the lip release and a very short lip opening time, suggesting that there was inadequate time to equilibrate, thus producing the lower pressure than its neighbor to the left. The next pressure pattern also may have too short of a stabilization time, but would appear to give a more accurate pressure estimate. Notice, too, that acoustics are visible on the shortest /p/ occlusion possibly indicating the effects of coarticulation. (These effects will not be explored further in this thesis.) Respiratory pumping. Respiratory pumping, or abrupt lung volume changes, is a major factor leading to inaccurate estimates of subglottal pressure from the oral pressure. The specific training of lip occlusion methodology to approximate subglottal pressure relies on the smooth, legato, nonpumping behavior of the subject, patient, or client. It is suggested that respiratory pumping may lead to changes in the shape of the oral pressure signal (Hertegård, Gauffin and Lindestad, 1995). Many researchers stress the importance of no changes in respiratory force across the syllable string produced to get accurate estimates of subglottal pressure (e.g., Ohala, 1974). In the current study, the subjects were instructed to use constant respiratory effort across the syllable string. The specific effects on oral pressure patterns due to respiratory pumping and therefore on estimates of subglottal pressure should be studied further.

97 86 Cheek compliance. During pilot work it was noticed that the compliance of the cheeks (how tight or how loose they are during the syllable repetition task) seemed to affect the shape of the oral pressure signal. Jaeger (1982) suggests that expansion of the cheeks during the /p/ occlusion causes oral pressure to be less than subglottal pressure due to a delay in the system equilibration. He measured the delay in equilibration with highly compliant cheeks and low compliant cheeks (achieved by holding the cheeks firmly with the hands). It was concluded using a Pimmel s analysis that for a highly compliant system (where the cheek tissue is easily expanded by oral pressure), oral pressure may underestimate subglottal pressure by as much as 30% (Jaeger, 1982). This variable should be furthered explored in future studies of estimating subglottal pressure from oral pressure and may be related to small changes in the oral pressure signal (wavy oral pressure signal, rise of pressure during the occlusion). Lip protrusion and retraction will also cause volume changes in the vocal tract that would affect the oral pressures and need to be considered. Nasal inhalation. In addition, the researcher and clinician must be aware of nasal inhalations during the task. A nasal inhalation during the lip occlusion will alter the oral pressure and thus provide radically inaccurate estimates of subglottal pressure during and possibly after the inhalation. Figure 3.22 (see below) shows an example of two nasal inhalations in the circled region of the figure as well as in each of the other lip occlusions. Notice that after the second nasal inhalation, the oral pressure seems to increase slightly. However, the pressure signal gives no real indications of pressure equilibration that is trustworthy.

98 87 Calibration and response time of pressure transducer. As with any research study, it is important to have the equipment properly calibrated. When dealing with estimating subglottal pressure, Rothenberg (1982) urges the clinician and researcher to be aware of the response time of their pressure transducers. The response time, as defined by Rothenberg (1982), is the amount of time it takes for 95% of a sudden complete change to happen. It is important to consider the response time of the system to determine if the transducer is capturing accurate representations of the oral pressure signal. In the current study, the response time of the pressure transducer was found to be around 10 milliseconds (it may be shorter due to the crude method used to test response time). The response time needed to show changes created by the lips to faithfully capture oral pressure signals that are rectangular shaped is at least 25 milliseconds, which is well within the response time of the system. Length of oral pressure tube. The oral pressure tube should be long enough to capture the pressure in the mouth but short enough that the tube not be occluded by the tongue. The pressure tube may be thought to affect phonation; however, Till, Jafari, Crumley, and Law-Till (1992) found that the presence of the oral pressure tube did not significantly change measures of jitter, shimmer, harmonics-tonoise ratio, and intensity when /pa/ was produced. Finding the ideal length of the oral pressure tube was difficult for some subjects. When the pressure tube was too long, the open tip rested against the tongue, resulting in visually lower oral pressure signals. When the pressure tube was too short, it was touching the teeth.

99 88 Anecdotally, one subject reported that when the pressure was determined to have the ideal shape by the researcher, the tube was under his tongue. With one subject, a recording utilizing two different length oral pressure tubes was made. Figure 3.21a shows the pressure signal for a tube that was placed between the teeth and cheek. This tube was shorter than the tube used in Figure 3.21b. In the latter, the pressure tube is longer and the tip of the tube is touching the tongue. If the tube were too short, a problem encountered in this study was that the saliva entered the tube (see Figure 3.22). If the tube is too long, the pressures may be reduced because the tongue may occlude the end of the tube. The tube needs to be placed between the upper and lower teeth to see the acoustic pressures on the oral pressure signal. When the tube only extends to the lips, the acoustic pressures on the pressure signal during the vowel are not easily visible (Figure 3.21a /mim/ syllables). The /mim/ syllables in Figure 3.21a should look like the /mim/ syllables in Figure 3.16c, namely reduced with acoustic vibrations on the signal. In Figure 3.21b the pressures are reduced compared to the pressure of the standard production condition of Figure 3.21c (notice scale changes from -10 to 20 cm H2O in the top figure to -5 to 10 cm H2O in the bottom figure).

100 89 Figure Oral Pressure Signals Comparing Differences in Oral Pressure Signals when Varying Oral Pressure Tube Length. Pressure signals for the velar leak task from subject F3 (first and last syllables are standard production condition and middle syllables are /mim/. a. Pressure signal when the oral pressure tube was too short with the open tip between the teeth and gums. The pressure tube may also have been occluded with saliva as noted by the greater than expected increase in pressure for the /mim/ syllables. b. Pressure signal when the oral pressure tube was too long and the tip of the oral pressure tube was occluded by the tongue. The pressure signals are reduced, which is particularly visible in the /mim/ syllables. c. Pressure signal when the tube is the correct length, between the lips and not occluded by the tongue. Saliva in the tube. During the current study, two female subjects (one not used in the analysis section herein because analysis of this subject s recordings was not completed.) used oral pressure tubes that became occluded with saliva. Shipp (1973) noted this issue with his subjects, and warned about ensuring that the tube does not become occluded. There are two main characteristics of an occluded tube. The first is the oral pressure during the vowel does not return to baseline (atmospheric pressure). The second is that the oral pressure is not faithfully followed by the transducer, giving shapes that do not reach a plateau despite the flow indicating an equilibrated vocal tract. Figure 3.22 is an example of both of these phenomena. After the syllable begins, the pressure never returns to zero during the vowel. This is because the saliva in the tube prevents change away from the pressure positive. The oral pressure is obviously not followed faithfully due to the strange shapes displayed. The vertical

101 90 lines represent the moments of initial lip occlusion during the consonant. The pressure is increasing but never plateaus for the same reason the pressure does not return to baseline during the vowel. The flow in this example indicates that the vocal tract was occluded but because the oral pressure is not reaching a flat portion, it is impossible to accurately estimate subglottal pressure from this syllable string. As discussed earlier, the initial occlusion is followed midocclusion by a velar leak, seen as the triangular flow pulse that reaches a peak and goes back to zero flow. Figure Multi-Signal Example of Untrained Syllable with Highlighted Issues. Microphone, oral airflow, oral pressure, and EGG signals (from top to bottom) for a female subject (F4). The oral pressure tube is occluded, holding the pressure positive across the syllable string. The pressure is acted upon by the environment, namely the changing oral pressure from the consonant to the vowel. The vertical lines represent where the /p/ occlusion takes place. The pressure attempts to rise to a rectangular but cannot level out before the lips open again. The circle represents nasal inhalation. Note that the pressure does not drop below baseline because the occlusion prevents rapid change of the oral pressure. The arrows in the figure represent 2 of the 10 instances of velar leak during the lip occlusion. The possible velar leak is noted by an increase in the flow signal during the lip occlusion.

102 91 CONCLUSIONS The goal of this study was to use a standard CV-string gesture that creates oral pressures during lip occlusions that are thought to be accurate estimates of the prevailing subglottal pressure present during the adjacent vowel, and to explore a variety of non-standard gestures that might result in inaccurate subglottal pressure estimates in comparison to the standard, thereby providing further insight into the methodologies for acquiring subglottal pressures, a measure of significant importance in the clinic and for research. Relative to the discussion of accuracy of estimates of subglottal pressure from oral pressure, it is noted that all measured oral pressure values are valid pressures in the mouth during the syllable string when the pressure system is well calibrated and is transducing the true pressure at the tip of the short tube because the tube is open and placed appropriately in the oral cavity. Concern for accuracy arises when those oral pressures are being used to estimate the subglottal pressures prevailing during the adjacent vowels. That is, accurate oral pressures can be used to make inaccurate estimates of subglottal pressure depending on the technique used by the speaker. Rectangular shaped oral pressure signals during smoothly produced /pv/ strings have relatively constant pressures in the mouth during the /p/ lip occlusion, indicating that pressure equilibration throughout the respiratory airway has taken place, and thus one can have high confidence that the pressure values in the oral cavity are accurate estimates of subglottal pressure during the vowel. When the shape of the oral pressure signal is non-rectangular, meaning that the pressure in the mouth is changing during the /p/ lip occlusion because some moving structure is causing a relatively abrupt volume change somewhere in the airway or there is a leak between the lips or through the velopharyngeal port, there becomes concern as to whether the measured oral pressure should be used to estimate subglottal pressure.

103 92 In the current study, lip leak, velar leak, and lack of time to equilibrate the system caused estimates of subglottal pressure to be inaccurate (lower than estimates of subglottal pressure from the standard production condition). Rate, if not increased so much as to prevent equilibration, and linguistic stress did not appear to create unacceptable estimates of subglottal pressure from oral pressure in the current study. Initially, rates between 1.4 and 4.8 syllables per second tended to provide the most rectangular shaped oral pressure signals. As long as the lips were closed long enough to allow for full equilibration, the lip closed quotient did not appear to be a factor in pressure accuracy if the shapes were rectangular. Inaccurate pressures were generally associated with triangular and rounded shaped oral pressure signals due to flow leaks while the standard production condition syllables were generally associated with rectangular or slightly angled oral pressure signals. When subjects were attempting to produce the standard production condition, the shape was most frequently rectangular. The shape was also most frequently rectangular for the /bip/ production (the use of /b/ instead of /p/ for the initial consonant) and the two syllable /pip / production. While the shape of the oral pressure signal is important to consider when attempting to make an accurate estimate of subglottal pressure from oral pressure, it is also important to consider the flow signal at every step of the process. If the flow signal returns to baseline (zero) during the /p/ occlusion (or /b/ occlusion) the pressure may then equilibrate during the /p/ occlusion, and then using that occlusion to estimate subglottal pressure would be appropriate. If the flow does not return to baseline, the likelihood of measuring an accurate estimation of the subglottal pressure is greatly reduced the further the flow is away from the baseline; the greater the shift of the flow away from baseline, the greater the leak. This assumes that the mask itself

104 93 has a leak-proof seal upon the face. If the mask itself is not firmly on the face, all measured flows will be inaccurate and too low. In addition to the flow returning to baseline during the occlusion, a rectangular shaped oral pressure signal needs to be maintained for a minimum of 16 milliseconds according to the results here. The duration of pressure rise during lip closing (or the left side of the oral pressure signal) must also increase within the response time of the oral pressure transducer. The current study also looked at other factors that may impact estimates of subglottal pressure. Intrinsic and environmental problems with the equipment may impact estimates of subglottal pressure. As previously mentioned, the response time of the transducer must be greater than the pressure rise time. Special attention should be paid to the oral pressure tube so that it is the proper length and does not become occluded. This study is limited in that subglottal pressure was not actually recorded. The standard production condition was designed based on the literature and careful consideration was given to literature that actually compared subglottal pressure measures to subglottal pressure estimates. The current study gives further information for clinicians and researchers in understanding the methodology related to estimating subglottal pressure from oral pressure. An obvious future direction for this research is actually measuring the subglottal pressure and the oral pressure simultaneously during these tasks to determine if the changes in the subglottal pressure are reflected in the oral pressure. Respiratory pumping, cheek compliance, and structural movements (jaw, tongue, velum, larynx, torso) are factors that may be present and ever changing in clinical populations and should be parametrically studied to see the potential changes in non-clinical and clinical populations. Other studies may consider the methods for training patients and others to optimize the potential for accurate pressure estimations. There is a

105 94 need for a more complete understanding of how to produce the CV strings and other utterances with the goal of accurate but non-invasive estimates of subglottal pressure from the oral air pressure.

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113 102 APPENDIX A Health, Speech, and Voice Questionnaire Approximating Subglottal Pressure from Oral Pressure: A Methodological Study Please check the box that applies to you. If you have a question about anything on this questionnaire please ask one of the experimenters. 1. Are you currently healthy? 2. Do you currently suffer from allergies that impact your voice production or your ability to breath? 3. Are you allergic to contact to gold-plated metal materials? 4. Do you currently smoke? 5. Does your voice today sound representative of your voice on a daily basis? 6. Have you ever received voice therapy? 7. Have you ever received speech therapy? 8. Are you currently receiving voice therapy? 9. Are you currently receiving speech therapy? 10. Have you ever received professional speech training? 11. Have you ever received professional voice training? 12. Are you currently receiving professional speech training? 13. Are you currently receiving professional voice training? Yes No Name: Date:

114 APPENDIX B Consensus Auditory-Perceptual Evaluation of Voice 103

115 104 APPENDIX C Flow Mask Calibration Calibration of an aerodynamic flow mask (Glottal Enterprise MSIF 2 S/N 2049S) was performed to ensure accuracy of flow measurements made during the experimental tasks. To perform the calibration of the aerodynamic flow mask, a two-way sweeper was set to push or pull air through a calibrated pneumotach (Rudolph ) and through the flow mask which was held flush to a mold. See Figure A1 for a schematic of the calibration setup. The airflow from the sweeper was adjusted using the line valve and the bleed valve to change (increase when pushing air and decrease when pulling air) the voltage in increments of approximately 0.5 volts within the range of 0 and 6.62 and 0 and The amount of flow through the pneumotach was represented by the voltage output of the pressure transducer (Validyne, MP 45-16). See Table A1 for the Validyne pressure transducer settings. The amount of pressure drop across the mask was represented by the voltage on the second voltage meter (Hewlett Packer 973A). This pressure drop is linearly related to the flow through the mask. The voltage readings were noted from the two voltmeters simultaneously across the entire calibration task. Table A1. The settings of the Validyne pressure transducers (Validyne, MP 45-16). Parameter Setting Sensitivity Gain 15 mv/v Sensitivity Vernier 5.0 Filter 10 Hz Suppression Off Zero Balance high balance Suppressed Output Selected

116 105 Figure A1. Flow Calibration Setup. This figure illustrates the equipment arrangement for the flow calibration of the pneumotach mask. In the figure, the air was being pushed through the mask. In another calibration set up, the air was pulled through the mask so the direction of the airflow was opposite. Calibration runs revealed three distinct patterns of voltage outputs depending on the flow. Figure A2 compares the voltage outputs to the flow (cc/s) for the Glottal Enterprise s flow mask for flow values between and cc/s. A best-fit line was used to create an equation to convert the voltage obtained from the mask system to flow. When the flow is between and cc/s, the conversion from voltage to flow is Flow (cc/s) = * V , where V refers to voltage. When the flow is outside the range of and cc/s, the relationship between flow and voltage becomes quadratic. Namely, when flow is between and cc/s the equation becomes, Flow (cc/s) = * V * V , and when flow is

117 106 between and cc/s the equation becomes, Flow (cc/s) = * V * V , where V is voltage in both equations. Figure A2. Voltage of Flow Mask v. Flow from Glottal Enterprise Mask. Voltage of flow mask compared to flow from the Glottal Enterprise mask. The equation in this figure indicates a linear relationship between flow and voltage and is only valid between and cc/s. The relationship between flow and voltage becomes quadratic at more extreme flow values.

118 107 APPENDIX D Oral Pressure Pneumotach Calibration Calibration of an oral pressure transducer was performed to ensure accuracy of oral pressure measurements made during the experimental tasks. The calibration took place using a pressure source that created equal pressure in the transducer and manometer. The pressure source was created by the experimenter who applied pressure (positive or negative) to the pressure transducer and u-tube manometer. The pressure was held constant by crimping the flexible tubing while the measurements were taken. The voltage and manometer were read simultaneously for each pressure output by the pressure source. Positive and negative pressures were recorded until the output voltage was maximized. The setup for oral pressure calibration can be found in Figure A3. Figure A3. The Equipment Arrangement for the Oral Pressure Transducer Calibration of the Glottal Enterprise Mask.