How Well do Hearing Protectors Work? Compiled Field Hearing Protector Fit-Testing Results Lee D. Hager Hearing Conservation Specialist 3M Occupational Health and Environmental Safety Division

Two Data Sets Aggregated data Aggregated data –Data export from E-A-Rfit Case Study Case Study –Manufacturing facility –Application of fit testing

Aggregate HPD Fit Testing Data Source data Source data –2 companies –44 locations –3487 tests –7 invalid –3480 available Pure data harvest Pure data harvest –Company techs –No intervention Information extracted Information extracted –Product –PAR  L and R Information collected Information collected –NRR 1979 Information calculated Information calculated –Means –Standard deviations –80 th and 20 th Percentiles –Range

MIRE - E-A-Rfit Dual element microphone Dual element microphone Simultaneous measurement inside and outside HPD yields noise reduction (NR) Simultaneous measurement inside and outside HPD yields noise reduction (NR) Specially prepared/probed HPD Specially prepared/probed HPD –Surrogate for regular HPD Software provides Software provides –Stimulus ≈ dB –Calculation –Compensation  MIRE (objective NR) to REAT (subjective insertion loss) comparison  Effect of probe

Nine Products Included Productn Yellow Neon TM 576 FX TM 164 TaperFit 2 TM 72 Classic TM Small55 Classic TM Regular1665 Push-Ins TM 402 E-Z-Fit TM 22 UltraFit TM 480 E-A-Rcustom TM 44 Polyvinyl selected by about half of users

Binaural Difference Binaural difference insignificant Binaural difference insignificant –T-test paired 2 sample for means t stat = 1 Similar on all products Similar on all products No difference Right/Left No difference Right/Left Better Ear

Overall PAR Findings Variability immense Variability immense –Range from 29 to 39 dB –SD 5.5 to 7.7 –80 th %ile  16 to 26  All 80 th %ile “sufficient” for protection to <85 dB TWA with noise exposure as provided nNRR 1979 Mean PARSD 20 th %ile 80 th %ileRange Yellow Neon FX TaperFit Classic Sm Classic Reg Push-In E-Z-Fit UltraFit E-A-R custom

Comparison to Lab Tests Note: NRR 1979 = laboratory mean – 2 SD

Example PAR Distributions Classic Regular N = 1665 NRR1979 = 29 dB Mean = 30 dB SD = 6.8 dB 80 th = 37 dB 20 th = 24 dB UltraFit N = 480 NRR1979 = 25 Mean = 26 dB SD = 5.5 dB 80 th = 31 dB 20 th = 22 dB Note: scale on all charts 1 to 50 PAR on X; % of tests 0% to 15% on Y

Example PAR Distributions 2 PushIn N = 402 NRR1979= 28 Mean – 27 dB SD – 5.9 dB 80 th = 31 dB 20 th = 22 dB Yellow Neon N = 576 NRR1979 = 33 Mean = 29 dB SD = 6.5 dB 80 th = 35 dB 20 th = 24 dB

Case Study Diverse Mfg Site Diverse Mfg Site –Abrasives –Home Care Products –Building & Commercial Products –Construction & Home Improvement –Acoustical insulation –Surgical drape material –Electronic Matting –Personal care products Pilot project Pilot project –Plant employment est. 500 –N = 149 Objective: Identify Objective: Identify –Incorrect use/insertion –Physiologic incompatibility  Improper selection of HPD for earcanal size/shape

Initial Screen “First time good” Retraining Alternate HPD Total %25%16%100%

Post Intervention Selection

Post Intervention Survey 83% said this would help them better protect their hearing at work 83% said this would help them better protect their hearing at work 78% said this would help them better protect their hearing at home 78% said this would help them better protect their hearing at home 93% said the test was time well spent 93% said the test was time well spent 100% were satisfied with the HPD options provided for the test 100% were satisfied with the HPD options provided for the test

Conclusions Aggregate data PAR findings Aggregate data PAR findings –Variability overrides –Binaural difference  Present  No preference –Most distributions appear to approach normal  n ≥ 150  Center near NRR 1979  Individual outliers are people too Case study Case study –About 60% OK pre- intervention –100% OK post- intervention  25% needed retraining  16% using improper HPD Individual fit testing appears to be the only way to assess individual Individual fit testing appears to be the only way to assess individual –Sufficiency –Selection –Fit