Audiology Neurotology Originl Pper Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 Received: My 21, 213 Accepted fter revision: Septemer 12, 213 Pulished online: Decemer 19, 213 Avilility of Binurl Cues for Bilterl Implnt Recipients nd Listeners with nd without Preserved Hering in the Implnted Er René H. Gifford Michel F. Dormn Sterling W. Sheffield Kte Teece c Amy P. Olund c Deprtment of Speech nd Hering Science, Arizon Stte University, Tempe, Ariz., Deprtment of Hering nd Speech Sciences, Vnderilt University, Vnderilt Bill Wilkerson Center, Nshville, Tenn., nd c Deprtment of Otorhinolryngology, Myo Clinic, Rochester, Minn., USA Key Words Binurl cues Bilterl cochler implnt hering Hering preservtion ptients Astrct The purpose of this study ws to exmine the vilility of inurl cues for dult, ilterl cochler implnt (CI) ptients, imodl ptients nd hering preservtion ptients using multiple-seline, oservtionl study design. Speech recognition ws ssessed using the Bmford-Kowl- Bench Speech-in-Noise (BKB-SIN) test s well s the AzBio sentences [Sphr AJ, et l: Er Her 212; 33: 112 117] presented in multi-tlker le t +5 db signl-to-noise rtio (SNR). Test conditions included speech t with noise presented t (S N ), 9 (S N 9 ) nd 27 (S N 27 ). Estimtes of summtion, hed shdow (HS), squelch nd sptil relese from msking (SRM) were clculted. Though nonwwe of the suject groups consistently showed ccess to inurl cues, the hering preservtion ptients exhiited significnt correltion etween summtion nd squelch wheres the ilterl nd imodl prticipnts did not. Tht is to sy, the two effects ssocited with inurl hering summtion nd squelch were positively correlted only for the listeners with ilterl coustic hering. This finding provides evidence for the supposition tht implnt recipients with ilterl coustic hering hve ccess to inurl cues, which should, in theory, provide greter enefit in noisy listening environments. It is likely, however, tht the chosen test environment negtively ffected the outcomes. Specificlly, the sptilly seprted noise conditions directed noise towrd the microphone (mic) port of the ehind-the-er (BTE) hering id nd implnt processor. Thus, it is possile tht in more relistic listening environments for which the diffuse noise is not directed towrd the processor/hering id mic, hering preservtion ptients hve inurl cues for improved speech understnding. 213 S. Krger AG, Bsel Introduction There re numer of pulished studies documenting the respective enefits of ilterl cochler implnttion, imodl hering nd hering preservtion cochler implnttion. Severl studies hve documented summtion, hed shdow (HS), inurl squelch (lso commonly termed inurl unmsking) nd sptil relese from msking (SRM) for ilterl cochler implnt (CI) recipients [Schleich et l., 24; Litovsky et l., 26; Wckym et l., 27; Buss et l., 28; Zeitler et l., 28; Epen et l., 29]. Since inurl hering is not required for HS or E-Mil krger@krger.com www.krger.com/ud 213 S. Krger AG, Bsel 142 33/13/191 57$38./ René H. Gifford Vnderilt University, Deprtment of Hering nd Speech Sciences Vnderilt Bill Wilkerson Center Nshville, TN 37232 (USA) E-Mil rene.h.gifford @ Vnderilt.edu
SRM, the only effects tht re solely indictive of inurl hering re summtion nd squelch. In previous studies with ilterl-implnt recipients, squelch estimtes were quite smll in most cses rnging from.9 to 1.9 db for dptive or pseudodptive mesures [Schleich et l., 24; Litovsky et l., 26] nd 8 18 percentge points for fixed signl-to-noise rtio (SNR) mesures [Lszig et l., 24; Buss et l., 28; Epen et l., 29; Verhert et l., 212]. In contrst to ilterl-implnt users, imodl listeners, without preserved hering in the implnted er, hve exhiited greter vriility nd generlly more modest estimtes of the use of inurl cues. In met-nlysis of 13 studies exmining dult imodl listeners, Schfer et l. [27] reported significnt imodl summtion (imodl vs. CI lone) of 14 percentge points cross studies for fixed SNR mesures. For dptive speech reception thresholds (SRTs), oth Gifford nd Dormn [212] nd Morer et l. [212] demonstrted 3-dB summtion effects for 11 nd 15 dult imodl listeners, respectively. Estimtes of inurl squelch for imodl listeners hve een much less frequently reported thn wht hs een typiclly reported in the literture for ilterl-implnt recipients. Schfer et l. [27] evluted 3 studies [Tyler et l., 22; Dunn et l., 25; Morer et l., 25] in met-nlysis reporting squelch s the performnce difference for the CI lone with noise directed to the hering id (HA) S N HA versus the imodl condition in the sme noise configurtion (S NHA ). Using this, they clculted men squelch estimte of 1.1 percentge points cross the 3 studies, found to e not sttisticlly significnt. Using the sme squelch clcultion for squelch in n dptive SRT, Morer et l. [212] reported significnt estimtes of squelch rnging from 2.6 to 3.6 db, over two test sessions. They reported, however, tht these estimtes were lrgely driven y the results for 2 imodl prticipnts who demonstrted much etter speech recognition performnce with the HA over the implnted er. listeners hve demonstrted similr mgnitude of HS effect to ilterl-implnt recipients, ut with different estimtes cross ers, s expected, given the symmetry in performnce cross the HA nd CI ers. In met-nlysis of 6 studies referencing the CI er nd 3 studies referencing the HA er, Schfer et l. [27] showed significnt men estimtes of n HS of 17.4 percentge points for the implnted er nd 61.1 percentge points for the HA er. Unilterl-implnt recipients with preserved hering in the implnted er (hering preservtion ptients) hve een shown to exhiit significnt enefits for speech recognition with vrious noise sources [Dunn et l., 21; Gifford et l., 21; Dormn et l., 212; Gifford et l., 213; Rder et l., 213], horizontl-plne locliztion [Dunn et l., 21] nd preserved interurl time differences [Gifford et l., 213]. Thus, there is some evidence tht these ptients hve ccess to inurl cues. However, no pulished study hs ttempted to compre these ptients to ptients with ilterl CIs nd ptients with imodl hering regrding the vilility of inurl cues. The hypothesis underlying this project ws tht implnt recipients with ilterl coustic hering would exhiit significntly greter summtion nd squelch thn either ilterl CI ptients or imodl listeners (who do not hve preserved hering in the implnted er). Our hypothesis ws driven y our finding of ccess to interurl time difference cues [Gifford et l., 213] in hering preservtion ptients nd the fct tht interurl spectrl mismtch, cused y disprte electrode insertion depths nd electrode-to-neurl interfces for ilterl recipients, hs een shown to negtively ffect squelch nd summtion [Yoon et l., 212]. Thus, the primry ojective of the study ws to exmine the vilility of inurl cues for dult ilterl CI recipients nd imodl listeners, oth with nd without preserved hering in the implnted er. Mterils nd Methods Sujects Demogrphic informtion for the 81 study prticipnts is shown in tles 1 3 for the 3 ilterl, 35 imodl nd 16 hering preservtion prticipnts, respectively. Vriles provided include ge t testing, gender, implnt type, experience with implnts, ided Speech Intelligiility Index t 6 db SPL s provided y the Audioscn Verifit rel-er mesures nd Consonnt Nucleus Consonnt (CNC, [Peterson nd Lehiste, 1962]) monosyllic word recognition performnce t 6 dba. Of note is tht not ll of the implnted electrodes for the hering preservtion were specificlly designed for hering preservtion purposes. Nevertheless, with minimlly trumtic surgicl techniques nd ptients hving more preopertive hering to potentilly preserve, postopertively we re going to e encountering more clinicl ptients with mesurle, nd idle, hering in the implnted er. For the hering preservtion ptients, the inclusion criteri specified udiometric thresholds of 8 db hering level or etter, t 25 Hz. This criterion ws sed on two fctors. The first ws the hlf-gin rule, s the mximum lowfrequency gin for most in-the-er (ITE) HAs is pproximtely 4 db. The second sis for this criterion ws tht previous studies hve shown tht the mjority of the electrocoustic stimultion- or imodl-sed enefit is derived from coustic hering t 25 Hz [Henry nd Ricketts, 23; Dwson et l., 24; Zhng et l., 21]. Prticipnts rnged in ge from 19 to 9 yers with men ge of 6.5 yers. Of 3 ilterl prticipnts, 26 received their implnts in sequentil surgeries. For ll 81 prticipnts, there ws n verge of 4.6 yers (rnge.5 21. yers) experience with the first implnt. For the sequentil ilterl prticipnts, the verge ex- 58 Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 Gifford/Dormn/Sheffield/Teece/Olund
Tle 1. Bilterl prticipnt demogrphic informtion including ge t testing, yers of electric experience for the 1st nd 2nd implnts, implnts, processors nd CNC monosyllic word recognition (% correct) in the 1st CI, 2nd CI nd in the ilterl condition Suject Age Yers exp 1st CI Yers exp 2nd CI Implnts Processors CNC 1st CI CNC 2nd CI CNC ilterl 1 5 3.3 2.6 CI24RE(CA) 2 Freedom 2 88 8 84 2 69 13.3 8.9 CI22M, CI24RCA Freedom 2 76 72 72 3 56 4.9 2.9 CI24RE(CA) 2 Freedom 2 88 8 84 4 46 1.5 4.1 C1.2, HR9K Pltinum BTE, Hrmony 66 5 78 5 59 9.9 4.8 CI24RE(CA) 2 Freedom 2 56 72 9 6 52 8.8 2.7 CII, HR9K Hrmony 2 8 44 92 7 59 19.7 7.6 CI22M, CI24RE(CA) Freedom 2 6 22 7 8 53 4.6 2.7 CI24RE(CA) 2 Freedom 2 74 8 84 9 22 3.4 3.4 CI24RE(CA) 2 Freedom 2 98 72 94 1 19 1.7 1.7 CI24RE(CA) 2 Freedom 2 98 9 98 11 47 21. 3.1 CI22M explnted-reimplnted CP81 2 6 5 8 CI24RE(CA), CI512 12 19 9.2 4. CI24RCS, CI24RE(CA) Freedom 2 74 66 92 13 75 5.6 1.4 CI24RE(CA), CI512 Freedom, CP81 76 76 86 14 63 19.6 1.2 CI22M, CI512 Freedom, CP81 66 88 94 15 51.6.5 HR9K 2 Hrmony 2 8 78 92 16 48 2.8 1.5 CI24RE(CA) 2 Freedom 2 8 68 84 17 62 6.6 1.4 HR9K 2 Hrmony 2 7 48 8 18 59 7.1.7 HR9K 2 Hrmony 2 82 7 9 19 67 2.5 1.2 CI24RE(CA) 2 Freedom 2 92 84 92 2 65 3.7 3. HR9K 2 Hrmony 2 96 82 96 21 62 8. 2.9 CI24RE(CA) 2 Freedom 2 36 56 58 22 6 2.4 2.1 Sont (H) 2 Opus2 2 74 74 78 23 37 1.1.9 CI512 2 CP81 2 94 9 96 24 63.9.7 CI512 2 CP81 2 46 46 72 25 55 7.5 2. CI24RE(CA), CI512 CP81 2 74 88 92 26 29 8.3 8.1 HR9K 2 Hrmony 2 42 68 78 27 45 8.5 8.5 Sont (H) 2 Opus2 2 84 78 86 28 61 2.8.6 Sont (H) 2 Opus2 2 64 46 72 29 5 9.3 9.3 Comi4+ (H) 2 Tempo+ 2 84 66 9 3 5 2.1 1. Sont (H) 2 Opus2 2 48 4 4 Men 51.8 7. 3.2 N/A N/A 73.5 67.5 83.1 SD 14.3 5.5 2.7 N/A N/A 16.6 17.3 12.4 Prticipnts who were simultneously implnted re shded in old. SD = Stndrd devition; Yers exp = yers of experience; N/A = not pplicle. perience with the second implnt ws 3.2 yers (rnge.5 9.3 yers) with men difference etween the two implnts of 4.4 yers (rnge.1 18.4 yers). Though the CNC monosyllic-word recognition scores re not demogrphic in nture, they were included here to chrcterize outcomes for wht is generlly considered the most commonly reported metric for English-speking recipients. More detil will e provided for CNC monosyllic-word recognition in the Results section. Individul nd men udiogrms for the nonimplnted ers of the unilterl-implnt recipients, with nd without preserved coustic hering in the implnted er, re shown in figure 1. Figure 1 displys individul nd men postopertive udiogrms for the implnted er for the prticipnts with preserved coustic hering in the implnted er. Audiogrms were otined for ll prticipnts immeditely prior to experimenttion. Me t h o d s Speech perception ws ssessed during one or two visits, depending upon listener preference, using recorded stimuli presented in sound-treted ooth t clirted level of 6 dba. For the 3 prticipnts preferring to prticipte over two test sessions, the period etween sessions ws etween 1 dy nd 1 week. Prticipnts used their everydy CI progrms nd were not permitted to mnipulte settings during testing. For Nucleus implnt recipients, ll prticipnts used the EVERYDAY setting which mkes use of the defult directionl microphone (mic) setting with the ddition of Autosensitivity nd Adptive Dynmic Rnge Optimiztion [Dwson et l., 24]. Test conditions for the Speech-in- Noise (SIN) testing included speech t with noise presented t (S N ), 9 (S N9 ) nd 27 (S N 27 ). All three listening conditions were completed for ech individul er s well s for the i- Avilility of Binurl Cues for CI Recipients nd Listeners Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 59
Tle 2. prticipnt demogrphic informtion including ge t testing, yers of electric experience, implnt, processor, ided Speech Intelligiility Index (SII) t 6 db SPL nd CNC monosyllic word recognition (% correct) in the HA, CI nd imodl conditions Suject No. Age yers Yers exp CI Implnt Processor Aided SII CNC HA CNC CI CNC imodl 1 76 2.1 CI24RE(CA) Freedom 26 22 54 8 2 82 1. CI24RE(CA) Freedom 51 28 64 48 3 39 4.8 CI24RCA Esprit 3G 21 38 84 96 4 74 6.2 CI24RE(CA) Freedom 4 84 84 5 64 1.9 HR9K Hrmony 22 8 9 6 66 1.5 CI24RE(CA) Freedom 1 9 9 7 58 5.5 HR9K Hrmony 19 9 78 8 7 4.8 CI24RCA Freedom 28 92 86 9 82 1.8 CI24RE(CA) Freedom 22 2 68 6 1 65 1.3 CI24RE(CA) Freedom 12 9 8 11 77.6 CI24RE(CA) Freedom 29 24 84 84 12 76 1. CI24RE(CA) Freedom 17 14 5 6 13 34.8 CI24RE(CA) Freedom 36 1 8 84 14 9 1. CI24RE(CA) Freedom 36 2 74 84 15 5.5 HR9K Hrmony 4 3 88 88 16 76 13.2 CI24RE(CA) Freedom 18 6 74 74 17 47 1.7 CI24M Freedom 15 6 72 82 18 41 3.2 HR9K Hrmony 7 88 82 19 52.6 CI512 CP81 43 54 98 98 2 64.8 CI512 CP81 2 8 84 86 21 78 5.6 CI24RE(CA) Freedom 2 2 52 68 22 69 2.1 CI24RE(CA) Freedom 35 26 92 9 23 74 5.9 CI24RE(CA) Freedom 15 8 76 24 79.9 CI24RE(CA) Freedom 16 1 5 72 25 84 7.3 Comi4+ Tempo+ 6 78 68 26 62.6 CI24RE(CA) Freedom 15 46 72 27 68 6.4 CI24RCA Freedom 21 18 94 9 28 72 5.3 CI24RE(CA) Freedom 28 6 92 88 29 86.8 CI512 CP81 33 22 38 64 3 68 1.9 CI512 CP81 23 68 84 31 68 3.5 HR9K Hrmony 37 18 74 8 32 72 3.4 CI24RE(CA) Freedom 15 76 84 33 73 2.2 CI512 CP81 28 3 91 94 34 79 1.7 CI24RCA CP81 38 34 6 78 35 64 5.3 HR9K Hrmony 4 6 9 96 Men 68. 3.6 N/A N/A 24.2 12.4 76.3 8.5 SD 13.5 3.2 N/A N/A 11.4 13.9 15.8 11.2 lterl, est-ided condition (ilterl, imodl or CI + ilterl HAs). For unilterl-implnt recipients wering HAs in one or oth ers, HA udiility ws verified for 6-dB-SPL speech immeditely prior to experimenttion using rel-er mesurements with NAL-NL1 prescriptive trgets [Dillon et l., 1998]. Prticipnts for whom HAs were undershooting trget udiility y >5 db t one or more frequencies hd their HAs reprogrmmed to mtch NAL-NL1 trgets. For prticipnts whose own HAs could not e djusted due to lck of reserve gin or incomptiility with NOAH progrmming softwre, lortory stock HAs (Phonk Nid III UP with dectivted Sound Recover, i.e. nonliner frequency compression) were progrmmed nd used for testing purposes. This occurred for 6 of the imodl sujects (18, 23, 24, 25, 32 nd 33). For these 6, testing ws only completed with the stock HAs progrmmed to NAL-NL1 trget udiility. For BKB-SIN, the SNR-5 or the SNR t which pproximtely 5% correct performnce would e expected ws recorded for ech condition. Two pired lists (e.g. 1A/B nd 2A/B) were presented for ech listening condition with the verge SNR-5 cross the pired lists reported s men performnce per prticipnt. For the AzBio sentences t +5 db SNR, performnce ws recorded in percent words correct. Two 2-sentence lists 6 Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 Gifford/Dormn/Sheffield/Teece/Olund
2 non-ci er Hering preservtion non-ci er Hering preservtion CI er Hering level (db) 4 6 8 1 12.125.25.5 1 2 4 8.125.25.5 1 2 4 8.125.25.5 1 2 4 8 Frequency (khz) c Fig. 1. Individul nd men udiometric thresholds (in db) otined on the dy of testing for the nonimplnted ers of the imodl nd hering preservtion ptients s well s the implnted er of the hering preservtion ptients. Error rs represent ± 1 stndrd devition. Tle 3. Hering preservtion prticipnt demogrphic informtion including ge t testing, yers of electric experience, implnt, processor, ided Speech Intelligiility Index (SII) t 6 db SPL in oth the implnted nd nonimplnted ers nd CNC monosyllic word recognition (% correct) in the following conditions: HA in implnted er (ipsi HA), HA in nonimplnted er (contr HA), CI only, CI + ipsi HA, CI + contr HA nd CI + ilterl HAs Suject No. Age yers Yers exp CI Implnt Processor Aided SII non-ci er Aided SII CI er CNC ipsi HA CNC contr HA CNC CI only CNC CI + ipsi HA CNC CI + contr HA CNC CI + ilterl HA 1 71 1.1 Hyrid L24 Hyrid Freedom 31 24 24 26 68 82 74 78 2 7 4.7 CI24RCA Freedom 18 6 1 94 9 98 94 3 69 1. Hyrid S8 Hyrid Freedom 57 44 16 5 42 74 78 82 4 52.7 CI512 CP81 46 9 6 54 98 96 98 98 5 49 4.5 CI24RE(CA) Freedom 3 1 4 4 9 9 96 98 6 79 1.7 CI24RE(CA) Freedom 12 16 26 8 92 96 94 7 61 2.1 Hyrid L24 Hyrid Freedom 32 34 21 48 76 94 9 88 8 61 1. CI512 CP81 19 6 1 3 84 82 8 84 9 45 1.4 Sont (H) Opus2 3 6 2 44 82 84 82 84 1 53 4. Hyrid S8 Hyrid Freedom 38 34 28 36 44 6 62 8 11 58 6.4 CI24RCA CP81 31 16 18 24 82 86 84 86 12 52 2. Hyrid S8 Hyrid Freedom 32 12 12 48 62 58 86 86 13 34 4.1 CI24RCA Esprit 3G 35 9 2 28 8 84 88 9 14 52 1.4 Hyrid L24 Hyrid Freedom 44 36 26 52 76 9 88 88 15 77.6 Sont (H) Opus2 22 12 14 48 56 46 56 16 83.9 CI422 CP81 29 15 12 26 42 4 46 Men 58.9 2.4 N/A N/A 31.6 18.1 1.6 31.6 7.8 78.8 8.4 83.3 SD 12.5 1.8 N/A N/A 11.2 12.4 1.23 16.1 2.7 16.1 17.4 14. were run for ech listening condition with the verge performnce cross the two lists recorded for ech prticipnt. Listening conditions were counterlnced cross prticipnts in ech listener group with the list numers chosen in qusi-rndom mnner. In ddition to the SIN testing, CNC word recognition ws lso ssessed for ll 81 sujects for ech er individully s well s in the ilterl, est-ided condition. For the hering preservtion sujects, dditionl listening conditions were tested including HA in the implnted er (ipsilterl HA), CI plus n ipsilterl HA, CI plus contrlterl HA (commonly termed the imodl condition), s well s CI plus ilterl HAs (i.e. ilterl est-ided). All speech stimuli were presented t clirted level of 6 dba. Avilility of Binurl Cues for CI Recipients nd Listeners Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 61
R e s u l t s 1 For most sequentilly implnted recipients, the etter-performing er ws the first implnted er. For 2 of the 26 of the sequentilly implnted ilterl recipients (77% of the study ilterl popultion), the first implnted er ws the etter-performing er (i.e. sujects 1 7, 11 13, 15 2, 22 24, 28 nd 29). Out of these 2 prticipnts, 3 (6, 7 nd 17) exhiited sttisticlly significnt CNC word recognition performnce for the 1st implnted er sed on inomil distriution model [Thornton nd Rffin, 1978]. Of the 6 sequentilly implnted ilterl recipients for whom the 1st implnted er did not exhiit the est performnce (i.e. sujects 5, 8, 14, 21, 25 nd 26), 3 demonstrted significntly poorer performnce with the 1st implnted er using the inomil distriution sttistic [Thornton nd Rffin, 1978]. All sequentilly implnted ptients reported hving first implnted their poorer-hering er on the sis of preopertive udiometric thresholds nd/or speech recognition performnce. Except for the 3 sujects demonstrting significntly poorer performnce with the 1st implnted er, ll of them reported preference for the 1st implnted er. CNC Word Recognition As shown in tles 1 3, CNC word recognition performnce ws otined for ll 81 prticipnts in ech individul er condition nd the ilterl, est-ided condition. Men implnt only performnce cross ll 81 prticipnts ws 72.3% with rnge of 26 98% correct. 1 Considering the poorer-hering er for ll prticipnts, men CNC word recognition ws 35.3% with rnge of 9% with the lowest scores elonging to the unilterlimplnt recipients nonimplnted ers. Considering the ilterl, est-ided condition (i.e. ll devices, oth ers) for ll 81 prticipnts, men CNC word recognition ws 82.% with rnge of 4 98% correct. For CNC word recognition, two-wy, repeted-mesures nlysis of vrince (ANOVA) ws completed with the suject group (imodl, ilterl nd hering preservtion groups) nd listening condition (etter er, poorer er nd ilterl est-ided) s vriles. For this nlysis, the etter-hering er for the hering preservtion ptients ws defined s the implnt plus the ipsilterl HA (see tle 3 ) nd the ilterl est-ided condition included oth ers with ll ville devices. In other words, the ilterl est-ided condition included the implnt plus ilterl HAs for the hering preservtion sujects. The ANOVA reveled significnt effect of suject group [F (2, 78) = 21.1, p <.1], listening condition [F (2, 78) = 437.7, p <.1] nd significnt interction [F (4) = 65., p <.1]. Post hoc multiple comprisons using the Holm- Sidk test reveled no significnt difference cross the 3 suject groups for the etter-hering er (p >.26 for ll comprisons). Considering the ilterl est-ided condition, there ws lso no significnt difference cross the 3 groups (p >.24 for ll comprisons). Not unexpectedly, however, there ws significnt difference for the poorerhering er, with the ilterl sujects chieving significntly higher levels of word recognition thn oth the imodl (t = 14.7, p <.1) nd the hering preservtion sujects (t = 7., p <.1). The hering preservtion sujects scored significntly higher thn the imodl sujects (t = 4.7, p <.1) for the poorer-hering er which reflects lower (i.e. etter) udiometric thresholds in the nonimplnted ers for the hering preservtion prticipnts ( fig. 1 ) nd ssocited higher (i.e. etter) ided Speech Intelligiility Index vlues (see tles 2, 3 ). Summtion for CNC word recognition cn e estimted y sutrcting the score for the etter-hering er from the ilterl, est-ided score. Summtion estimtes were 6.1, 4.3 nd 4.4 percentge points for the ilterl, imodl nd hering preservtion sujects, respectively. Sttisticl nlysis ws completed for summtion estimtes cross suject groups. A Kruskl-Wllis ANOVA on rnks ws completed s the ssumption of normlity ws not met. There ws no significnt difference [H (2) = 1.6, p =.45] cross the 3 suject groups for summtion oserved with CNC word recognition in quiet. Speech-in-Noise: S N With reference to the BKB-SIN scores shown in figure 2, men SNR-5 for the etter-hering er ws 6.8 db for ilterl, 7.2 db for imodl nd 7.4 db for hering preservtion sujects. Men SNR-5 for the poorer-hering er ws 1. db for ilterl, 19.3 db for imodl nd 15. db for hering preservtion sujects. For the est-ided condition, men SNR-5 ws 5.8 db for ilterl, 6.3 db for imodl nd 5.3 db for hering preservtion sujects. A two-wy ANOVA ws completed with listening condition nd suject group s the vriles. The nlysis reveled significnt min effect of listening condition [F (2) = 129.8, p <.1], suject group [F (2) = 23.5, p <.1] nd significnt interction [F (2) = 17.1, p <.1]. Post hoc nlysis using the Holm-Sidk sttistic showed no difference cross the 3 suject groups for either the etter-hering er or the est-ided condition (p >.11 for ll comprisons). There were significnt differences cross the suject groups for the poorer-hering er with ll suject groups eing significntly different from one nother (p <.1 in ll cses). With reference to the AzBio sentence recognition t +5 db SNR ( fig. 2 ), men performnce (in percent correct) for the etter-hering er ws 56.8% for ilterl, 49.2% for imodl nd 6.1% for hering preservtion sujects. Men performnce for the poorer-hering er ws 36.1% for ilterl, 5.7% for imodl nd 16.7% for hering preservtion sujects. For the est-ided condi- 62 Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 Gifford/Dormn/Sheffield/Teece/Olund
Bilterl Hering preservtion SNR-5 (db) 25 2 15 1 5 5 S N 1st CI 2nd CI Bilterl CI HA CI + ipsi HA Contr HA CI + ilt HA AzBio +5 db (% correct) 1 8 6 4 2 S N 1st CI 2nd CI Bilterl CI HA CI + ipsi HA Contr HA CI + ilt HA Fig. 2. Box nd whisker plots for BKB-SIN (SNR-5; ) nd AzBio t +5 db (% correct; ) for the S N listening condition. The ox extends from the 25th to the 75th percentile with the horizontl line in the middle representing the medin. The whiskers extend from the minimum to the mximum vlue for ll individul dt thus displying the rnge of scores for ny given condition. Summtion (db) 1 8 6 4 2 2 4 Bilterl Hering preservtion Suject group Bilterl Hering preservtion Summtion (percentge points) 6 4 2 2 Bilterl Hering preservtion Suject group Fig. 3. Box nd whisker plots for BKB-SIN (in db; ) nd AzBio t +5 db (in percentge points; ). The ox extends from the 25th to the 75th percentile with the horizontl line in the middle representing the medin. The whiskers extend from the minimum to the mximum vlue for ll individul dt thus displying the rnge of scores for ny given condition. tion, men performnce ws 65.5% for ilterl, 58.6% for imodl nd 65.9% for hering preservtion sujects. As with the BKB-SIN results in the S N condition, twowy ANOVA ws completed with listening condition nd suject group s the vriles. The nlysis reveled significnt min effect of listening condition [F (2, 231) = 116.2, p <.1], suject group [F (2, 2) = 15.9, p <.1] nd significnt interction [F (2, 4) = 4.4, p =.2]. Holm-Sidk post hoc nlysis showed no difference cross the 3 groups for either the etter-hering er or the est-ided condition (p >.1 for ll comprisons). There were significnt differences cross the groups for the poorerhering er, with ll 3 groups eing significntly different from one nother (ilterl vs. imodl, p <.1; ilterl vs. hering preservtion, p =.1; imodl vs. hering preservtion, p =.4). Summ t ion Estimtes of summtion were gthered from figure 2 s the difference etween the etter-hering er nd estided condition. Box nd whisker plots re shown in figure 3. For BKB-SIN ( fig. 3 ), men summtion ws 1., Avilility of Binurl Cues for CI Recipients nd Listeners Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 63
BKB-SIN (db SNR-5) BKB-SIN (db SNR-5) 25 2 15 1 5 5 1 25 2 15 1 5 5 1 Bilterl 1st CI 2nd CI 1st CI 2nd CI 1st CI 2nd CI Bilterl 1st CI 2nd CI CI HA CI HA CI HA CI HA.9 nd 1.9 db for the ilterl, imodl nd hering preservtion prticipnts, respectively. Individul estimtes of summtion rnged from 3.5 to 7.3 db for ilterl, 2 to 4 db for imodl nd 1.5 to 6. db for hering preservtion prticipnts. A one-wy ANOVA reveled no difference cross the sujects groups in terms of summtion effects (F (2) = 1.7, p =.18). For AzBio sentence recognition t +5 db ( fig. 3 ), men summtion ws 8.5, 9.5 nd 5.4 percentge points for the ilterl, imodl nd hering preservtion sujects, respectively. Individul estimtes of summtion rnged from 13 to 52 percentge points for ilterl, 13 to 25 percentge points for imodl nd 12 to 42 percentge points for hering preservtion prticipnts. As with BKB-SIN, one-wy ANOVA reveled no difference cross the groups (F =.62, p =.54). Speech-in-Noise: Sptilly Seprted Listening Conditions Figure 4 displys ox nd whisker plots for BKB-SIN scores (SNR-5) for the ilterl, imodl nd hering preservtion sujects for the sptilly seprted listening conditions (S N 9 nd S N 27 ). Figure 5 displys the sme ox nd whisker plots s figure 4 ut for AzBio sentence recognition t +5 db SNR. With the dt shown in figures 2, 4 nd 5, we re le to clculte estimtes of HS, SRM nd squelch. Hed Shdow Estimtes of HS were clculted s follows: BKB-SIN (db SNR-5) c 25 2 15 1 5 5 1 CI er Contr CI er Contr CI er Contr Best EAS CI + ipsi HA Listening condition, noise direction Hering preservtion Contr HA Fig. 4. Box nd whisker plots for BKB-SIN (SNR-5) for the ilterl ( ), imodl ( ) nd hering preservtion sujects ( c ) for the sptilly seprted listening conditions with S N 9 nd S N 27. Bilterl Sujects HS for 1st CI = score for 1st CI (noise to 2nd CI) score for 1st CI (noise to 1st CI). HS for 2nd CI = score for 2nd CI (noise to 1st CI) score for 2nd CI (noise to 2nd CI). Sujects HS for CI er = score for CI er (noise to HA er) score for CI er (noise to CI er). HS for HA er = score for HA er (noise to CI er) score for HA er (noise to HA er). Hering Preservtion Sujects HS for CI er = score for CI er (noise to non-ci er) score for CI er (noise to CI er). HS for non-ci er = score for non-ci er (noise to CI er) score for non-ci er (noise to non-ci er). Estimtes of HS re shown in figure 6 for BKB-SIN nd AzBio t +5 db SNR, respectively. For BKB-SIN, men HS for the ilterl CI recipients ws 7.6 nd 5.3 db for the 1st nd 2nd implnted ers, respectively. Men HS for the imodl listeners ws 7.6 nd 3.3 db for the CI nd HA ers, respectively. Men HS for the hering preservtion sujects ws 5. nd 4.8 db for the CI nd non- CI ers, respectively. A two-wy ANOVA with suject 64 Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 Gifford/Dormn/Sheffield/Teece/Olund
1 8 6 4 2 1 8 6 4 2 1 8 6 4 2 Percent correct Percent correct Percent correct Bilterl 1st CI 2nd CI 1st CI 2nd CI 1st CI 2nd CI Bilterl 1st CI 2nd CI CI HA CI HA CI HA CI HA Hering preservtion For AzBio t +5 db SNR, men HS for the ilterl CI recipients ws 34.7 nd 32.9 percentge points for the 1st nd 2nd implnted ers, respectively. Men HS for the imodl listeners ws 36.6 nd 7.1 percentge points for the CI nd HA ers, respectively. Men HS for the hering preservtion sujects ws 22. nd 11.8 percentge points for the CI nd non-ci ers, respectively. A two-wy ANOVA completed with suject group nd listening condition reveled significnt effect of suject group [F (2, 231) = 8.7, p <.1], significnt effect of listening condition [F (2, 2) = 14., p <.1] nd significnt interction [F (2, 2) = 8.2, p <.1]. Holm-Sidk post hoc nlysis reveled tht the HS estimtes were significntly greter for the ilterl-implnt recipients thn for the imodl (t = 3.4, p =.1) nd hering preservtion (t = 3.8, p =.2) prticipnts. There ws no significnt difference cross the 3 suject groups for the etter-hering er (p >.5 for ll comprisons). There were significnt differences cross the suject groups for the poorer-hering er with ech group eing significntly different from the others (ilterl vs. imodl, p =.3; ilterl vs. hering preservtion, p =.3; imodl vs. hering preservtion, p =.1). Sptil Relese from Msking Estimtes of SRM were clculted s follows: Bilterl Sujects SRM for 1st CI = score for 1st CI (noise to 2nd CI) score for 1st CI (noise t ). SRM for 2nd CI = score for 2nd CI (noise to 1st CI) score for 2nd CI (noise t ). c CI er Contr CI er Contr CI er Contr CI + ilt HA CI + ipsi HA Contr HA Listening condition, noise direction Fig. 5. Box nd whisker plots for AzBio sentences t +5 db (percent correct) for the ilterl ( ), imodl ( ) nd hering preservtion sujects ( c ) for the sptilly seprted listening conditions with S N 9 nd S N 27. group nd listening condition (poorer vs. etter er) reveled no effect of suject group [F (2, 231) = 1.2, p =.3], significnt effect of listening condition [F (2, 2) = 7.7, p =.6] nd no interction [F (2, 2) = 2.4, p =.9]. Thus there ws no difference in HS cross the suject groups, ut estimtes were significntly greter for the etterhering er. Sujects SRM for CI er = score for CI er (noise to HA er) score for CI er (noise t ). SRM for HA er = score for HA er (noise to CI er) score for HA er (noise t ). Hering Preservtion Sujects SRM for CI er = score for CI er (noise to non-ci er) score for CI er (noise t ). SRM for non-ci er = score for non-ci er (noise to CI er) score for non-ci er (noise t ). For All Suject Groups, SRM in the Best-Aided Condition SRM for est-ided = score for est-ided condition (noise to poorer er) score for est-ided condition (noise t ). Avilility of Binurl Cues for CI Recipients nd Listeners Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 65
Bilterl Hering preservtion HS (percentge points) 3 2 1 1 Poorer Better Poorer Better Poorer Better Bilterl Suject group, er Hering preservtion HS (percentge points) 1 8 6 4 2 Poorer Better Poorer Better Poorer Better Bilterl Suject group, er Hering preservtion Fig. 6. Box nd whisker plots displying estimtes of HS for BKB-SIN (in db; ) nd AzBio t +5 db SNR (in percentge points; ) for the poorer er, etter er nd est-ided conditions. Fig. 7. Box nd whisker plots displying estimtes of SRM for BKB-SIN (in db; ) nd AzBio t +5 db SNR (in percentge points; ) for the est-ided condition. SRM (db) 12 1 8 6 4 2 2 4 Bilterl Hering preservtion Suject group Bilterl Hering preservtion SRM (percentge points) 5 4 3 2 1 1 2 Bilterl Hering preservtion Suject group Estimtes of SRM in the est-ided condition re shown in figure 7 for BKB-SIN nd AzBio t +5 db SNR, respectively. For BKB-SIN, men SRM for the ilterl CI recipients ws 3.5 nd 3.8 db for the 1st nd 2nd implnted ers, respectively, nd 5.1 db for the ilterl est-ided condition. Men SRM for the imodl listeners ws 5.7 nd 1.5 db for the CI nd HA ers, respectively, nd 4.9 db for the imodl est-ided condition. Men SRM for the hering preservtion sujects ws 4. nd 2.1 db for the CI nd non-ci ers, respectively, nd 3.8 db for the est-ided condition (CI + ilterl HA). A one-wy ANOVA completed for SRM oserved reveled no effect of suject group for the etter-hering er [F (2) = 1.4, p =.25] or for the est-ided condition [F (2) = 1.3, p =.29], ut significnt effect of group for the poorer-hering er [F (2) = 11.1, p <.1]. For the poorer-hering er, post hoc testing (Holm-Sidk) reveled tht the SRM of imodl sujects ws significntly poorer thn tht of oth ilterl (t = 4.5, p =.2) nd hering preservtion (t = 3., p =.4) sujects, ut tht the ilterl nd hering preservtion groups were not different (p =.49). For AzBio t +5 db SNR, men SRM for the ilterl CI recipients ws 2.9 nd 16.3 percentge points for the 1st nd 2nd implnted ers, respectively, nd 2.4 percentge points for the est-ided condition. Men SRM for the imodl listeners ws 19.9 nd 2.7 percentge points for the CI nd HA ers, respectively, nd 14.1 percentge points for the est-ided condition. Men SRM for the hering preservtion sujects ws 8.4 nd 11.5 percentge points for the CI nd non-ci ers, respectively, nd 1. percentge points for the est-ided condition. A one-wy ANOVA completed for SRM oserved reveled no effect of suject group for the etter-hering er [F (2) = 2.2, p =.12] or for the est-ided condition [F (2) =.14, p =.87], ut significnt effect of group for the poorer-hering er [F (2) = 13.3, p <.1]. For the poorer- 66 Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 Gifford/Dormn/Sheffield/Teece/Olund
Squelch (db) 25 2 15 1 5 5 1 Poorer Better Poorer Better Poorer Better Bilterl Hering preservtion Suject group, er Bilterl Hering preservtion Squelch (percentge points) 8 6 4 2 2 4 Poorer Better Poorer Better Poorer Better Bilterl Hering preservtion Suject group, er Fig. 8. Box nd whisker plots displying estimtes of SRM for BKB-SIN (in db; ) nd AzBio t +5 db SNR (in percentge points; ) for the est-ided condition. hering er, Holm-Sidk post hoc nlysis reveled tht the SRM estimtes were significntly greter for the ilterl-implnt recipients thn for oth the imodl (t = 5.2, p <.1) nd the hering preservtion (t = 2.2, p =.49) prticipnts. S qu e l ch Estimtes of squelch were clculted s follows: Bilterl Sujects Squelch for 1st CI = score for ilterl CI (noise to 2nd CI) score for 1st CI (noise to 2nd CI). Squelch for 2nd CI = score for ilterl CI (noise to 1st CI) score for 2nd CI (noise to 1st CI). Sujects Squelch for CI er = score for imodl (noise to HA er) score for CI er (noise to HA er). Squelch for HA er = score for imodl (noise to CI er) score for HA er (noise to CI er). Hering Preservtion Sujects Squelch for CI er = score for est ided (noise to non- CI er) score for CI er (noise to non-ci er). Squelch for non-ci er = score for est ided (noise to CI er) score for non-ci er (noise to CI er). Squelch estimtes for BKB-SIN nd AzBio t +5 db re shown in Figures 8 nd, respectively. For BKB-SIN, ecuse lower score represents etter performnce, squelch estimtes otined vi the ove-referenced equtions yielded negtive numers for positive squelch nd positive numers for negtive squelch. For ese of reporting nd interprettion, ll squelch estimtes for the BKB- SIN metric hve een inverted, such tht positive squelch will e reported s positive numers nd vice vers. For BKB-SIN, men squelch for the ilterl CI recipients ws.9 nd 2.3 db for the 1st nd 2nd implnted ers, respectively. Men squelch for the imodl listeners ws.7 nd 1.4 db for the CI nd HA ers, respectively. Men squelch for the hering preservtion sujects ws.5 nd 7.2 db for the CI nd non-ci ers, respectively. A two-wy ANOVA completed with suject group nd listening condition reveled n effect of suject group [F (2) = 12.3, p <.1], listening condition [F (1) = 99.9, p <.1] nd significnt interction [F (2, 1) = 26.7, p <.1]. Holm- Sidk post hoc nlysis reveled tht the squelch estimtes were significntly lower for the ilterl-implnt recipients thn oth the imodl (t = 3.4, p =.1) nd hering preservtion (t = 3.8, p =.2) prticipnts n effect tht ws driven primrily y the non-ci ers for the imodl nd hering preservtion prticipnts. There ws no significnt difference cross the 3 suject groups for the etter-hering er (p >.6 for ll comprisons). There were significnt differences cross the suject groups for the poorer-hering er with ll 3 groups eing significntly different from one nother (ilterl vs. imodl, p <.1; ilterl vs. hering preservtion, p <.1; imodl vs. hering preservtion, p =.6). Avilility of Binurl Cues for CI Recipients nd Listeners Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 67
For AzBio sentence recognition t +5 db SNR, men squelch estimtes for the ilterl CI recipients were 6.1 nd 7.2 percentge points for the 1st nd 2nd implnted ers, respectively. Men squelch for the imodl prticipnts ws.2 nd 32.7 percentge points for the CI nd HA ers, respectively. Men squelch for the hering preservtion sujects ws 1.7 nd 42.1 percentge points for the CI nd non-ci ers, respectively. Sttisticl nlysis reveled significnt effect of suject group [F (2) = 5.7, p =.4], significnt effect of listening condition [F (1) = 47.2, p <.1] nd significnt interction [F (2, 1) = 11.9, p <.1]. Post hoc nlysis using the Holm-Sidk test reveled tht squelch ws significntly lower for the ilterl-implnt recipients thn oth the imodl (t = 2.8, p =.17) nd the hering preservtion (t = 3., p =.3) prticipnts s discussed ove with BKB-SIN, this outcome ws primrily driven y the non-ci ers for the imodl nd hering preservtion prticipnts. There ws no difference cross the 3 suject groups for the etterhering er (p >.25 for ll comprisons). There ws significnt difference cross the suject groups for the poorer-hering er with the ilterl group demonstrting significntly less squelch thn oth imodl listeners (p <.1) nd hering preservtion (p <.1) prticipnts. D i s c u s s i o n The results of this study were lrgely consistent with previous reports in the literture exmining vilility of inurl cues for dults with ilterl implnts. Men estimtes of HS for the implnted ers were consistent with previous reports in the literture rnging from 5. to 7.6 db for the pseudodptive BKB-SIN (e.g. Gntz et l. [22], Muller et l. [22], Schon et l. [22], Schleich et l. [24] nd Litovsky et l. [26]) nd 22. 36.6 percentge points for AzBio sentences t +5 db (e.g. Buss et l. [28] nd Epen et l. [29]). Men estimtes of squelch for the ilterl-implnt ptients were lso consistent with previous reports rnging from.9 to 2.3 db for the BKB-SIN mesure [Schleich et l., 24; Litovsky et l., 26] nd 6.1 7.2 percentge points for AzBio sentence recognition t +5 db SNR [Buss et l., 28; Epen et l., 29]. Summtion ws lso roughly consistent with previous reports for ilterlly implnted dults, though slightly lower in this study, with men summtion eing 1. db for BKB-SIN [Schleich et l., 24; Litovsky et l., 26; Zeitler et l., 28] nd 8.5 percentge points for AzBio sentences t +5 db SNR [Buss et l., 28; Epen et l., 29]. Thus the results of our study with simultneous nd sequentil ilterl-implnt recipients replicte the findings of previous reports most of which exmined ilterl recipients who hd received their implnts in the sme surgery. Considering these effects for the unilterl-implnt prticipnts, estimtes of HS, squelch nd SRM were not significntly different from wht ws oserved in the ilterl-implnt recipients when considering the implnted er. Estimtes of summtion were lso not different for the imodl nd hering preservtion sujects with coustic hering compred to the ilterl-implnt users. Considering the nonimplnted er for imodl nd hering preservtion prticipnts, estimtes of squelch were significntly greter thn wht ws oserved for ny of the implnted ers. The reson for this seemingly prdoxicl finding is relted to the underlying ssumption of symmetry in performnce cross ers. Tht is to sy, squelch provides informtion regrding improvement in speech understnding provided y dding n er with poorer SNR. For the imodl nd hering preservtion ptients, the improvement gined y dding the implnted er ws disproportionlly greter thn the improvement gin for ilterl-implnt users, given tht the CI er yields significntly greter speech understnding thn the nonimplnted ers. So the squelch estimtes for the imodl nd hering preservtion listeners simply do not provide n ccurte description s the er with the etter SNR ws neither the etter-performing er nor equivlent in performnce to the er with the poorer SNR. For this reson, Morer et l. [212] suggested the use of modified eqution for descriing imodl squelch effects s follows: squelch = imodl score (noise to non-ci er) CI score (noise to non-ci er) This is the eqution we used to descrie squelch for the implnted ers of imodl nd hering preservtion ptients for which men estimtes were.7 nd.5 db for BKB-SIN nd.2 nd 1.7 percentge points for AzBio sentences t +5 db. Given tht some hering preservtion ptients hve een shown to exhiit some preserved sensitivity to interurl time differences for low-frequency stimuli [Gifford et l., 213], it is resonle to sk why the hering preservtion ptients in our study filed to exhiit summtion nd, more importntly, squelch. A numer of potentil explntions for this finding re likely. One my relte to the degree of summtion effects tht could e used in the listening prdigm used here. As seen in fig- 68 Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 Gifford/Dormn/Sheffield/Teece/Olund
Squelch (db) 1 8 6 4 2 2 4 BKB-SIN r =.54 p =.4 Squelch (percentge points) 25 2 15 1 5 5 1 15 2 25 AzBio +5 r =.71 p =.1 2 2 4 6 8 Summtion (db) 2 15 1 5 5 1 15 2 25 Summtion (percentge points) Fig. 9. Individul squelch estimtes of hering preservtion ptients re plotted s function of summtion for BKB-SIN (db; ) nd AzBio +5 db (percentge points; ). Digonl dshed lines represent liner regression function representing the Person correltion coefficient shown in ech pnel. ure 3, the rnge of mesurle summtion for the hering preservtion ptients ws quite vrile, with some exhiiting summtion effects of 6 db for BKB-SIN nd 42 percentge points for AzBio t +5 db. By completing correltion nlyses for summtion nd squelch for ll listener groups in our study, there ws significnt positive correltion oserved etween summtion nd squelch for the hering preservtion ptients (BKB-SIN r =.54, p =.4; AzBio r =.71, p =.1) s displyed in figure 9. The correltion nlyses for the ilterl nd imodl prticipnts, however, were not significnt for either speech metric. One could contend tht these dt support our hypothesis tht implnt recipients with preserved coustic hering in the implnted er should hve greter ccess to inurl cues. In other words, those implnt recipients with ilterl coustic hering who exhiit summtion effects in ourexperimentl prdigm were lso more likely to enefit from inurl squelch thn oth ilterl-implnt recipients nd imodl listeners. Another possile reson for the lck of inurl effects for the hering preservtion ptients is the chosen test environment. Our study incorported the clssic experimentl design for clculting HS nd squelch including the following: S N, S N 9 nd S N 27. Presenting noise directly to the side of the listener, s in S N 9 nd S N 27, is not the est choice of conditions given the mic port loction for CI processors nd ehind-the-er (BTE) HAs. Festen nd Plomp [1986] demonstrted tht the BTE mic loction negtively ffected SNR y 2 db when speech ws presented t compred to ±9. In other words, the physicl SNR t the mic will e lower (i.e. poorer) with noise originting t 9 or 27 compred to hving oth speech nd noise t. As 14 of the 16 hering preservtion ptients were Nucleus implnt recipients, the premise of mic loction ffecting the outcomes in the chosen test environment my pper flwed given tht directionl mics hve een used in cochler processors since the introduction of the Freedom TM processor. In description of the polr ptterns of the Freedom processor, Ptrick et l. [26] showed tht with speech t nd noise t 9, the signl t 9 ws still pproximtely 2-dB higher thn the signl t zimuth. Thus, the experimentl setup hd the potentil to rtificilly inflte estimtes of HS nd negtively impct estimtes of squelch for ll suject groups in our study s well s in ll previous studies for which noise ws presented directly to the side of the listener. In more diffuse-noise condition s experienced in everydy listening environments it my e the cse tht hering preservtion ptients would enefit from inurl squelch. Finlly, nother possile reson for the lck of inurl effects for the hering preservtion ptients ws the heterogeneity of electrode rrys nd the rnge of hering thresholds in the implnted er. As mentioned in the Sujects section, not ll of the electrodes implnted for her- Avilility of Binurl Cues for CI Recipients nd Listeners Audiol Neurotol 214;19:57 71 DOI: 1.1159/3557 69
ing preservtion were specificlly designed for this purpose. Neither the Nucleus perimodiolr rrys nor the Sont H (i.e. stndrd) electrodes were designed with hering preservtion in mind, despite hving met the inclusion criteri for our study. Further investigtion will continue to determine whether the purportedly trumtic electrodes yield inurl enefit, nmely summtion nd squelch, for implnt recipients with preserved hering. Co n c l u s i o n We hypothesized tht preserved coustic hering in the implnted er ffording ilterl coustic hering would yield greter ccess to inurl cues for the hering preservtion prticipnts. Our findings could not reject the null hypothesis. Although our study did not provide evidence for the vilility of inurl cues to ptients with hering preservtion, the findings my hve een confounded y the test conditions. Specificlly, the sptilly seprted noise conditions directed noise towrd the mic port of the BTE HA nd implnt processor; this negtively ffects the SNR compred to the S N condition [Festen nd Plomp, 1986]. Given tht 12 of the 16 hering preservtion listeners exhiited some inurl summtion, it is possile tht greter ccess to inurl cues my e present in more relistic listening environments. Acknowledgements The reserch reported here ws supported y grnt R1 DC944 from the NIDCD to the first uthor. Portions of this dt set were presented t the 28 conference of the Americn Auditory Society in Scottsdle, Ariz., USA nd the 13th Symposium on Cochler Implnts in Children (CI211) in Chicgo, Ill., USA. 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