How Well do Hearing How Well do Hearing Protectors Work? Protectors Work?

Compiled Field Hearing Compiled Field Hearing Protector Protector Fit-TestingFit-Testing Results Results

Lee D. HagerLee D. HagerHearing Conservation SpecialistHearing Conservation Specialist

3M Occupational Health and Environmental Safety 3M Occupational Health and Environmental Safety DivisionDivision

517.647.5882517.647.5882leehager@cablespeed.comleehager@cablespeed.com

Two Data SetsTwo Data Sets

Aggregated dataAggregated data– Data export from E-A-RfitData export from E-A-Rfit

Case StudyCase Study– Manufacturing facilityManufacturing facility– Application of fit testingApplication of fit testing

Aggregate HPD Fit Testing Aggregate HPD Fit Testing DataData

Source dataSource data– 2 companies2 companies– 44 locations44 locations– 3487 tests 3487 tests – 7 invalid7 invalid– 3480 available3480 available

Pure data harvestPure data harvest– Company techsCompany techs– No interventionNo intervention

Information extractedInformation extracted– ProductProduct– PARPAR

L and RL and R

Information collectedInformation collected– NRRNRR19791979

Information calculatedInformation calculated– MeansMeans– Standard deviationsStandard deviations– 8080thth and 20 and 20thth Percentiles Percentiles– RangeRange

MIRE - E-A-RfitMIRE - E-A-Rfit Dual element microphoneDual element microphone Simultaneous measurement Simultaneous measurement

inside and outside HPD yields inside and outside HPD yields noise reduction (NR)noise reduction (NR)

Specially prepared/probed Specially prepared/probed HPDHPD– Surrogate for regular HPDSurrogate for regular HPD

Software provides Software provides – Stimulus ≈ 85-90 dBStimulus ≈ 85-90 dB– CalculationCalculation– CompensationCompensation

MIRE (objective NR) to REAT MIRE (objective NR) to REAT (subjective insertion loss) (subjective insertion loss) comparisoncomparison

Effect of probeEffect of probe

Nine Products IncludedNine Products Included

Product n

Yellow NeonTM 576

FXTM 164

TaperFit 2TM 72

ClassicTM Small 55

ClassicTM Regular 1665

Push-InsTM 402

E-Z-FitTM 22

UltraFitTM 480

E-A-RcustomTM 44

Selection Distribution

Yellow Neon16%

FX5%

TaperFit 22%

Classic Small2%

Classic Reg47%

Push-In12%

E-Z-Fit1%

UltraFit14%

E-A-Rcustom1%

Polyvinyl selected by about half of users

Binaural DifferenceBinaural Difference

Binaural difference insignificantBinaural difference insignificant– T-test paired 2 sample for means t T-test paired 2 sample for means t

stat = 1stat = 1 Similar on all productsSimilar on all products No difference Right/LeftNo difference Right/Left

Right - Left PAR

0

50

100

150

200

250

300

350

400

Better Ear

Overall PAR FindingsOverall PAR Findings

Variability Variability immenseimmense– Range from Range from

29 to 39 dB29 to 39 dB– SD 5.5 to 7.7SD 5.5 to 7.7– 8080thth %ile %ile

16 to 2616 to 26 All 80All 80thth %ile %ile

“sufficient” “sufficient” for for protection to protection to <85 dB TWA <85 dB TWA with noise with noise exposure as exposure as providedprovided

n NRR1979

Mean PAR SD

20th

%ile80th

%ile Range

Yellow Neon 576 33 29 6.5 35 24 39

FX 164 33 26 5.8 31 21 34

TaperFit 2 72 29 24 7.2 29 16 34

Classic Sm 55 29 31 7.7 38 26 34

Classic Reg 1665 29 30 6.8 37 24 36

Push-In 402 28 27 5.9 31 22 38

E-Z-Fit 22 28 22 6.6 27 18 29

UltraFit 480 25 26 5.5 31 21 34

E-A-Rcustom 44 21 26 6.8 29 22 31

Comparison to Lab TestsComparison to Lab TestsNRR 1979 to (PAR - 1SD)

0

5

10

15

20

25

30

35

Yellow Neon FX TaperFit 2 Classic Small Classic Reg PushIn EZFit Ultrafit E-A-Rcustom

PAR - 1 SD NRR 1979

Note: NRR1979 = laboratory mean – 2 SD

Example PAR DistributionsExample PAR DistributionsClassic RegularN = 1665NRR1979 = 29 dBMean = 30 dBSD = 6.8 dB80th = 37 dB20th = 24 dB

Classic Reg

0%

2%

4%

6%

8%

10%

12%

14%

5048464442403836343230282624222018161412108642

PAR (dB)

% o

f te

sts

UltraFit

0%

2%

4%

6%

8%

10%

12%

14%

5048464442403836343230282624222018161412108642

PAR (dB)

% o

f te

sts

UltraFitN = 480NRR1979 = 25Mean = 26 dBSD = 5.5 dB80th = 31 dB20th = 22 dB

Note: scale on all charts 1 to 50 PAR on X; % of tests 0% to 15% on Y

Example PAR Distributions 2Example PAR Distributions 2PushInN = 402NRR1979= 28Mean – 27 dBSD – 5.9 dB80th = 31 dB20th = 22 dB

Push-In

0%

2%

4%

6%

8%

10%

12%

14%

5048464442403836343230282624222018161412108642

PAR (dB)

% o

f te

sts

Yellow Neon

0%

2%

4%

6%

8%

10%

12%

14%

5048464442403836343230282624222018161412108642

PAR (dB)

% o

f te

sts

Yellow NeonN = 576NRR1979 = 33Mean = 29 dBSD = 6.5 dB80th = 35 dB20th = 24 dB

Case StudyCase Study Diverse Mfg SiteDiverse Mfg Site

– AbrasivesAbrasives– Home Care ProductsHome Care Products– Building & Commercial Building & Commercial

ProductsProducts– Construction & Home Construction & Home

Improvement Improvement – Acoustical insulation Acoustical insulation – Surgical drape Surgical drape

material material – Electronic Matting Electronic Matting – Personal care products Personal care products

Pilot projectPilot project– Plant employment Plant employment

est. 500est. 500– N = 149N = 149

Objective: IdentifyObjective: Identify– Incorrect Incorrect

use/insertionuse/insertion– Physiologic Physiologic

incompatibilityincompatibility Improper selection Improper selection

of HPD for earcanal of HPD for earcanal size/shapesize/shape

Initial ScreenInitial Screen““First First time time goodgood

””

RetrainiRetrainingng

AlternatAlternate HPDe HPD

TotalTotal

8888 3737 2424 149149

59%59% 25%25% 16%16% 100%100%

Screening Test

8837

24

“First time good”

Retraining

Alternate HPD

Post Intervention SelectionPost Intervention Selection

Post Intervention SurveyPost Intervention Survey

83%83% said this would help them said this would help them better protect their hearing at workbetter protect their hearing at work

78%78% said this would help them said this would help them better protect their hearing at homebetter protect their hearing at home

93%93% said the test was time well said the test was time well spentspent

100%100% were satisfied with the HPD were satisfied with the HPD options provided for the testoptions provided for the test

ConclusionsConclusions Aggregate data PAR Aggregate data PAR

findingsfindings– Variability overridesVariability overrides– Binaural differenceBinaural difference

PresentPresent No preferenceNo preference

– Most distributions Most distributions appear to approach appear to approach normal normal n ≥ 150n ≥ 150 Center near NRRCenter near NRR19791979 Individual outliers are Individual outliers are

people toopeople too

Case studyCase study– About 60% OK pre-About 60% OK pre-

interventionintervention– 100% OK post-100% OK post-

interventionintervention 25% needed retraining25% needed retraining 16% using improper 16% using improper

HPDHPD Individual fit testing Individual fit testing

appears to be the appears to be the only way to assess only way to assess individualindividual– SufficiencySufficiency– SelectionSelection– FitFit