Field fit testing with E-A- Rfit Dual-Ear system on earmuff in China Yufei Liu / 3M China Min Yang / GD Province Hospital of China for Occupational Disease Prevention and Treatment NHCA Conference Feb. 2017, San Antonio
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3M E-A-Rfit TM Dual-Ear Validation System Personal Attenuation Rating (PAR) External Microphone Internal Microphone
About the PARs PAR PAR = binaural PAR value - binaural uncertainty PAR - baseline PAR - after training Initial PAR in Follow up visits The PAR obtained when a subject was first measured in this study, without coaching or intervention in anyway. The PAR obtained after training on the current assigned HPD. The PAR obtained from the retests which was done in a period after the first measurement, without coaching or intervention in anyway.
Test procedure Questionnaire Baseline / initial Completed No Hair cover fit under the earmuff? No PAR failed or Improper fitting No Yes PAR without hair covers Yes Train & refit (intervention group) Completed Refit, PAR w/ hair covers PAR failed or Poor improvement on skill No New HPD & refit Yes M. Yang, GD Province Hospital for Occupational Disease Prevention and Treatment, Y.F. Liu, 3M. Preparing for publication.
Four Visits Initial visit Measuring different fits in one work shift 6-month follow up visit 12-month follow up visit - Obtain PAR baseline; - Identify intervention group, and provide intervention; - Observe the impact of use of hair covers. Observe protection from different fits throughout the work shift. Observe the sustainability of the training effect from the last visit. Observe whether the earmuffs could provide sufficient protection (PAR 22 db) after a period of use.
Information about the surveyed factory Hot & humid High noise exposure 2015 average temperature of the city was 23 (74 F), the highest temperature was 37 (99 F), HIGH humidity. 3 different workshops were surveyed: - Group 1, 66 subjs, PAR pass criteria = 15 db; - Group 2, 123 subjs, PAR pass criteria = 22 db. Well trained, experienced earmuff users - Hearing conservation program has been in place for more than 10 years; - Earmuffs mandatory for more than 3 years; - Intensive training for workers.
General information about test subjects Service Year Years of use of HPD Noise exposure duration per working day in hours Education level Gender < 1 year 1 to 5 years 6 to 10 years > 10 years 2% 46% 26% 26% < 1 year 1 to 2 years 3 to 5 years > 6 years 2% 33% 22% 43% 100% 80~99% 50~79% 20~49% <20% 36% 50% 10% 3% 1% Grade school Junior high school High school Junior college or above 2% 54% 37% 7% Male Female 48% 52%
PARs - baseline Group 1, PAR pass criteria = 15 db, 100% pass Passed after training, 20 subjects, 16% PAR pass rate - Group 2 pass criteria = 22 db Failed, 4 subjects 3% 35 30 25 20 15 10 PAR baseline vs. labeled values 24 25 31 Passed, 99 subjects 81% 5 0 PAR - baseline 2- db corrected NRR 2- db corrected SNR
PAR (db) Effect of one-on-one training associated with fit testing 35 Intervention group, n=85 30 25 20 15 10 5 0 PAR Baseline PAR After training
PAR (db) 35 PARs obtained at different points in a single work shift (n = 39) 30 25 26 26 26 26 26 25 26 Subject A 20 15 10 19 14 17 14 15 20 17 Subject B Subject A 5 0 Time Subject B
PAR (db) Impact of use of hair cover (n=74) 38 out of 74 subjects (51%) were in intervention group, after training, the mean PAR improved from 21 db to 26 db when the hair covers were worn, P-value = 0 36 34 32 30 26 24 22 20 18 Impact on PARs of hair cover fitting under the earmuffs With hair cover Without hair cover Hair cover worn under the earmuff
Sustainability of training effectiveness n Mean (db) SD (db) P-Value Baseline (initial visit) 63 21 4.4 6-month follow up visit 63 23 4.0 0.01 After training (initial visit) 63 25 2.7 6-month follow up visit 63 23 4.0 0.00
Sustainability of training effectiveness n Mean (db) SD (db) P-value PAR baseline Initial PAR at 6-month follow up visit 22 23 4.1 3.6 0.16 PAR after training Initial visit Initial PAR at 6-month follow up visit 26 23 2.5 3.6 0.00 PAR baseline Initial PAR at 12-month follow up visit 22 25 4.1 4.1 0.00 PAR after training Initial visit Initial PAR at 12-month follow up visit 26 25 2.5 4.1 0.06
Conclusion Even though it is easier to fit earmuffs compared with fitting earplugs, fit testing can be valuable, and is highly recommended to verify the sufficiency of attenuation for earmuffs; One-on-one training together with fit testing was shown to improve PAR and helped to reduce the negative impact of use of hair covers; Good habit to follow the user instruction to obtain proper fit could help to maintain consistent, good protection; Since earmuffs are often used for long time periods, exceeding a year or more, repeated fit testing can be helpful to verify the protection throughout their useful life. M. Yang, GD Province Hospital for Occupational Disease Prevention and Treatment, Y.F. Liu, 3M. Preparing for publication.
Reference ANSI (1974). "Method for the Measurement of Real-Ear Protection of Hearing Protectors and Physical Attenuation of Earmuffs," Am. Natl. Stds. Inst., S3.19-1974, New York, NY. Berger, E. H., Voix, J., Kieper, R. W., & Le Cocq, C. (2011). Development and validation of a field microphone-in-real-ear approach for measuring hearing protector attenuation. Noise & Health, 13, 163-175. Gauger D, Berger EH (2004). A new hearing protector rating: the noise reduction statistic for use with A weighting (NRSA). Report for US Environmental Protection Agency. Approved by ANSI S12/WG11, E-A-R 04-01/HP, Indianapolis, IN. ISO (1994). "Acoustics - Hearing Protectors - Part 2; Estimation of Effective A- Weighted Sound Pressure Levels When Hearing Protectors Are Worn", Int. Org. for Std., ISO/ DIS 4869-2.2, Switzer land. www.3m.com/3m/en_us/worker-health-safety-us/safety-equipment/hearingconservation/hearing-protection-fit-testing/3m-earfit-user-support, Presentation of uncertainty/variability values