Selection of passive hearing protection · 2019. 12. 17. · SELECTION OF PASSIVE HEARING...

2018

DepartmentofDefenseHearingCenterofExcellence3/1/2018

Selectionofpassivehearingprotection

SELECTIONOFPASSIVEHEARINGPROTECTION

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Table of Contents SelectionofPassiveHearingProtection......................................................................................................4

1.0 Introduction.................................................................................................................................4

2.0 Background..................................................................................................................................4

3.0 Posterelements...........................................................................................................................5

A. Continuousnoiseattenuation.....................................................................................................5

B. Impulsivenoise............................................................................................................................7

C. Spatialawareness(localization)...................................................................................................8

4.0 SelectingHearingProtection.......................................................................................................9

A. Considerationsinselectingappropriatehearingprotection.......................................................9

B. DeterminingHazardousNoiseRequirements............................................................................11

C. DeterminingSpatialAwarenessNeeds......................................................................................11

5.0 Conclusion.................................................................................................................................11

References.................................................................................................................................................12

AnnexA.Acronyms....................................................................................................................................13

Acknowledgements...................................................................................................................................14


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Selection of Passive Hearing Protection

1.0 Introduction ThepurposeofthisguidebookistoexplainelementsoftheEvaluatedPassiveHearingProtectionDevice(HPD)postertoenablehearinghealthprofessionals,industrialhygienists,andsafetyprofessionalstobetterselecthearingprotectionappropriateforthenoiseenvironmentandhearingcriticaltasksServiceMembersperform.TheHPDslistedinthisguidebookhavebeenthoroughlyevaluatedforperformancebutdonotconstituteanapprovedHPDlist.

Goodhearingiscriticaltowarfighterperformance.Allwarfightersrelyonhearingtocommunicateamongindividuals,withinandbetweenunits,withhigherheadquarters,andoftenbetweenbattlespacesandotherServices.Warfightersalsorelyonhearingforsituationalawareness,suchasdeterminingthedirectionofgunfireorwhetheranenemyisapproaching.Manywarfightersworkinhazardousnoiseenvironmentseverydayoftheirmilitarycareer.Exposuretohazardousnoise,continuousand/orimpulsive,maycausesignificanthearinglossand/orhearingrelateddisabilities.Reducingtheriskofhearinglossisessential;whenengineeringandadministrativecontrolsarenotpossible,HPDsarerequired.

TraditionalpassiveHPDsaredesignedtoreducetheamountofhazardousnoisereachingtheinnerear.WhileprotectinghearingisanessentialqualityofallHPDs,somewarfightersrequireHPDsthatallowcriticalsoundstopassthroughthedevicetoallowforcommunicationcapabilitiesandsituationalawareness.Forexample,forceprotectionpersonnelmustbeabletocommunicatewithapproachingpeople,detectandidentifysounds,localizethedirectionofthesound,andworkwithintermittentnoisefromapproachingvehiclesorevengunfire.Assuch,researchersdesignedassessmentmethodstodeterminehowwellHPDsfunctiononthreefronts:continuousnoisesuppression;impulsivenoisesuppression;andsoundlocalization.

TheposterprovidesanoverviewofperformancecharacteristicsofpassivehearingprotectivedevicesthatincludesattenuationforcontinuousandimpulsivenoiseandtheeffecttheHPDhasontheuser’ssoundlocalizationperformance.Inthisguide,section2hasbackgroundinformation,section3reviewstheposterelements,andsection4providesguidanceonselectingproperhearingprotection.

2.0 Background WhenselectingHPDs,theworkingenvironment,typeofworkperformed,andthehearingcriticaltasksoftheworkmustbeconsidered.First,HPDsmustprovidetheappropriatelevelofprotectionforthenoiselevel.Louderenvironmentsdemandgreaterlevelsofattenuation,butoverprotectionmaymaketheuserfeelisolatedfromtheenvironmentanddecreasetheuser’ssituationalawareness.Whenselectinghearingprotection,factorsotherthannoiseattenuationmaybeconsideredsuchashowadeviceaffectshearingcriticaltasks,comfort,compatibilitywithotherequipmentandothernon-acousticalfactorslikeeaseofuseandcost.

Hearingcriticaltasksaretasksinwhichhearingistheonlysensethatcanperformthosetasks.Responsetothedetection,identification,locationofsound,orunderstandingspeechisoftentimesensitive,isusuallyrelatedtothesafetyofanoperation,andleadstothesuccessfulcompletionofanoperation.Examplesofhearingcriticaltasksaretalkingoverthetelephoneorradio,detectingenemy


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presenceinlowvisibilityenvironmentsorwhenvisionisobscured,anddeterminingthedirectionofenemygunfire.

TheEvaluatedPassiveHearingProtectionDevicesposterpresentspassiveHPDsthatdonotcontainnorallowconnectiontoelectronicsthatcansuppressnoise,connecttoradiosystems,orenhancehearingcriticalsounds.HPDshavebeendevelopedwiththosecapabilities;however,thesedevicesarenotnecessaryformanyjobsinthemilitary.Audiologists,industrialhygienists,andsafetyprofessionalscanassessworkplacesandmakerecommendationsforappropriateHPDsforeachtask.ThemostexpensiveormosttechnologicallyadvancedHPDisnotalwaysnecessary.ThebestHPDprovidesthenecessarylevelofprotection,fitswell,iscomfortabletowear,andallowsuserstohearcriticalsoundsnecessaryforthejob.Mostimportantly,itisusedbytheemployeeandworncorrectly.

3.0 Poster elements MarineCorpsSystemsCommandprovidedfundingforthestudyandselectedallthepassive

insertHPDs.TheAirForceResearchLaboratory(AFRL)performedtheHPDassessmentthatincludedcontinuousnoiseattenuation,impulsivenoiseattenuationandsoundlocalizationmeasurementsbywayofanaurallyguidedvisualsearchtask.EachHPDontheposterisdescribedwithaproductname,apictureofthedevice,andaNationalStockNumber(NSN)whenapplicable.TheperformancemetricsarealsodisplayedforeachHPDbywayofacoloredratingscale.Asquareisusedtorepresentthecoloredratingforcontinuousnoiseattenuation;acirclerepresentsthecoloredratingforimpulsivenoiseattenuation;andapentagonisusedtorepresentthecoloredratingforspatialawareness.

A. Continuous noise attenuation 1. ContinuousnoiseattenuationdatawascollectedinaccordancewithANSIS12.6-2008MethodA,

trained-subjectfit.a. NoiselevelreductionstatisticsforA-weighting(NRSA)versusNoiseReductionRating

(NRR)i. NRR,asinglenumberdescriptor,isawell-knownwayofestimatingthenoise

levelunderaHPD.EPAregulationsrequiremanufacturerstodisplaytheNRRon


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HPDlabels.However,theNRRwasdesignedtobesubtractedfromC-weightednoiselevelsandrequiresa7-dBspectraladjustmentbeappliedpriortosubtractingitfromA-weightednoiselevels.

ii. NoiselevelreductionstatisticsforA-weighting(NRSA)wasdesignedtobesubtracteddirectlyfromthemeasuredA-weightednoiseleveltoestimatethelevelofsoundattheearunderthehearingprotector.Themethodoffersseveraladvantagesoverthewell-knownNRR.Asstatedabove,theNRRwasdesignedtobesubtractedfromC-weightednoiselevels.NRSAeliminatesthisproblemwiththeNRRbysubtractingfromtheA-weightednoiselevels,whicharetypicallyknown.NRSAshouldnotbeusedwithnoiseenvironmentsthathavehighlevelsoflowfrequencycontentoriftheoverallsoundpressurelevelexceeds100dBA.AnotheradvantageofNRSAisthatitcalculatestwolevelsofprotectiontoindicatetherangeofperformanceachievedduringtheevaluation.Thisrangereflectsthevariationacrossthesubjectsinthetestpanel,providinginsightintohowhard/easythedevicemaybetofit.Themajorityofusers(80%)willachievetheperformancespecifiedbythelowervalueintherange,withonlythemostmotivatedproficientusers(20%)abletoachieveorexceedthehighervalue.

iii. PosterdisplaystheNRSAviaacolorcodeforthemajorityofusers(80%).1. Blue–30dBorgreater2. Green–20-30dB3. Yellow–10-20dB4. Red–10dBorless

HearingProtector

NRSA PosterRatings80% 20%

3MEARUltraFit 19 30 YellowAllenSoundSensor 17 30 YellowEarPlugzPCwithcord 17 31 YellowEarPlugzPCwithoutcord 16 29 YellowEtymoticER20ETY 14 20 YellowHearDefendersDF 19 29 YellowHearingArmor 16 30 YellowHowardLeightMax 29 29 GreenMoldexBattlePlugsClosed 19 30 YellowMoldexBattlePlugsOpen 10 19 RedMoldexPuraFit 33 41 BlueSensGardSG26 19 31 YellowSensGardSG31 23 33 GreenCombatArmsGen4Closed 23 29 GreenCombatArmsGen4Open 10 17 YellowSonicDefendersEP3Closed 18 31 YellowSonicDefendersEP3Open 12 20 YellowSonicDefendersEP4Closed 23 28 GreenSonicDefendersEP4Open 12 20 Yellow


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SonicDefendersEP7Closed 28 34 GreenSonicDefendersEP7Open 16 30 Yellow

2. ConsultserviceguidancewhenusingtheNRR.

B. Impulsive noise 1. Whenanticipatingexposuretoimpulsivenoisesuchasonafiringrange,personnelshould

choosehearingprotectionthathasbeenevaluatedforitscapabilitytoprotectagainstimpulsivenoisehazards.M16susuallygeneratemid-150dBPrangeattheshooter(buthighertothesides)anda105mmHowitzerexposescrewtolevelsfromthemid-160dBPrangetothelow-180dBPrangedependingonfiringconditions.WhenselectingHPDstoprotectagainstimpulsivenoise,choosethepeaksoundpressurelevelclosesttotheexpectedexposure.

a. Note:ImpulsivenoiseisthetermusedinMIL-STD-1474E,theDepartmentofDefenseDesignCriteriaStandardNoiseLimits.Thetermismorecurrentandissynonymouswithimpulsenoise.

b. Thebelowtablelistsdevicesandtheaverageimpulsivepeakinsertionlossdatafromblastmeasurements.ANSIS12.42-2010wasusedforthetestingmethodology.Theinsertionlossforeachearatimpulsivenoiselevelsat170dB,185dBand195dBiscontainedbelow.

c. Theposterdisplaysviaacolorcodetheimpulsivenoiseattenuationat170dB.i. Blue–30dBorgreaterii. Green–20-30dBiii. Yellow–10-20dBiv. Red–10dBorless

HearingProtector

PeakSoundPressureLevel PosterRatings170dB 185dB 195dB

3MEARUltraFit 36 35 36 BlueAllenSoundSensor 10 21 33 YellowEarPlugzPCwithcord 35 36 33 BlueEarPlugzPCwithoutcord 34 35 41 BlueEtymoticER20ETY 25 28 32 GreenHearDefendersDF 41 38 39 BlueHearingArmor 35 36 30 BlueHowardLeightMax 41 41 41 BlueMoldexBattlePlugsClosed 36 BlueMoldexBattlePlugsOpen 30 GreenMoldexPuraFit 54 41 41 BlueSensGardSG26 31 27 33 BlueSensGardSG31 28 20 29 GreenCombatArmsGen4Closed 40 BlueCombatArmsGen4Open 33 BlueSonicDefendersEP3Closed 28 28 33 GreenSonicDefendersEP3Open 26 28 32 GreenSonicDefendersEP4Closed 35 Blue


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SonicDefendersEPOpen 28 GreenSonicDefendersEP7Closed 41 41 41 BlueSonicDefendersEP7Open 28 34 40 Green

C. Spatial awareness (localization) 1. Spatialawarenesswasassessedusinganaurallyguidedvisualsearch.Thistaskdemonstrates

theimpactHPDshaveonthetimerequiredtoaccuratelylocatetheoriginofasound.Inthetest,subjectsaretestedinthreeconditions,(1)visualtargetwithoutauralguide,(2)visualtargetwithauralguide,nohearingprotector,and(3)visualtargetwithauralguideandhearingprotector.Withoutanauralguide,subjectsaverage12.2secondstofindthetarget.Withhearingprotection,subjectstakelongertofindatargetuntiltheauralguidepresentationlevelsarearound80dB.

a. Posterdisplaysthesearchtimewhenthepresentationlevelwasat40dBviaacolorcode.

i. Blue–4secondsorlessii. Green–4-7secondsiii. Yellow–7–10secondsiv. Red–10secondsorgreater

HearingProtector

TargetLevel(dBSPL) Total(30,40,60)

PosterRating15 30 40 60 80

3MEARUltraFit 12 11 5 4 28 RedAllenSoundSensor 10 8 5 5 22 YellowEarPlugzPCwithcord 13 11 5 5 29 RedEarPlugzPCwithoutcord 11 9 5 4 25 YellowEtymoticER20ETY 12 9 6 3 18 GreenHearDefendersDF 12 11 5 4 28 RedHearingArmor 10 9 5 3 24 YellowHowardLeightMax 12 12 8 6 33 RedMoldexBattlePlugsClosed -- -- -- -- -- --MoldexBattlePlugsOpen -- -- -- -- -- --MoldexPuraFit 12 13 12 6 37 RedSensGardSG26 10 7 4 5 21 GreenSensGardSG31 9 7 5 4 21 YellowSonicDefendersEP3Closed 12 8 4 4 24 YellowSonicDefendersEP3Open 12 11 6 4 21 GreenSonicDefendersEP4Closed -- -- -- -- -- --SonicDefendersEP4Open -- -- -- -- -- --SonicDefendersEP7Closed 13 12 5 4 30 RedSonicDefendersEP7Open 12 12 10 4 26 Red


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4.0 Selecting Hearing Protection Thechartbelowisadecisiontreethatwillassistinselectingthebesthearingprotectionfortheexpectednoiseexposureandthejobtask.TheHPDsdepictedintheposterandinthisguidebookarepassiveearplugsonly.Ifcommunicationinanoisehazardousenvironmentisessential,deviceswithadditionalcapabilitiesshouldbeusedasopposedtotheHPDsinthisdocument.

A. Considerations in selecting appropriate hearing protection

1. Noise environment a. Ahazardouscontinuousnoiseenvironmentiswheretheambientnoiselevellastsfor1

secondormore(usuallymuchlonger),butwhichcanbevariable,steadyorintermittentovertime.DoDI6055.12defineshazardoussteadystatenoiselevelsat85dBAtimeweightedaverage(TWA)orgreateroveran8-hourtimeframe.Shipboardengineeringspaces,generatornoiseandhelicopternoiseareexamplesofcontinuousnoise.i. Singlehearingprotectionshallbewornwhennoiselevelsmeetorexceed85dBA,

regardlessofduration.ii. TheDoDnoiseexposurecriteriontoreducetheriskofhearinglossorhearing

relateddisabilitiesis85dBAforadurationof8hourswitha3dBperdoublingexchangerate.Therefore,ifthenoiselevelincreasesto88dBAtheallowabledurationoftimeinnoise,ifunprotected,isreducedto4hours.

iii. Guidanceontheuseofearplugandearmuffcombinations,commonlyreferredtoasdoublehearingprotection,differsamongtheServices.Theterm“double”hearingprotectionismisleadingastheattenuationfromearplugandearmuffislessthan


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thearithmeticsumoftheirindividualattenuationvalues.Whenguidanceindicatesdoublehearingprotectionisneeded,theOccupationalSafetyandHealthAdministrationrecommendsadding5dBtothederatedNRRofthehearingprotectorwiththehighestNRRtodeterminetotalattenuationprovidedbytheearplugandearmuffcombination.Regardlessofwhetherusingsingleordoubleprotection,theservicemembersoremployee’stotalexposureshallbereducedtobelow85dBATWAforan8-hourworkday.

1. TheArmyHearingProgramrequiresuseofearplugsandhelmetorearplugsandearmuffswhensteadystatenoiselevelsare103dBATWAandupto108dBATWA.

2. TheRevisedInterimNavyMedicineHearingConservationProgramGuidancestatesareasorequipmentwheresoundpressurelevelsare96dBAorgreatershallrequiretheuseofdoublehearingprotectionthatattenuatesworkernoiseexposurebelowan8-hourTWAor85dBA.TheNavybasesdoublehearingprotectionupontheeffectivefieldderatedupperlimitofmostearplugsandearmuffs.

3. FortheAirForce,thehearingprotectorsprovidedmustbecapableofattenuatingworkernoiseexposurebelowaTWAof85dBA.Thethresholdforusingdualhearingprotectiondependsontheprotectorsselected.PerAirForceInstruction48-127,3dBshouldbeaddedtothehighestNRRoftheplugormufftoestimatecombinedprotectiverating.ConsultthelocalbioenvironmentalunitortheAirForceEnvironment,SafetyandOccupationalHealthService(ESOH)Centerforassistanceindeterminingtheappropriatehearingprotection.

3. Impulsivenoiseisashortdurationsoundlastinglessthan0.5seconds,containingoneormorepulses.Impulsivenoiseisconsideredhazardousifoneormoreofthepulsesexceeds140decibelspeak(dBP)orgreater.Gunshotsandmanualhammeringareexamplesofimpulsivenoise.

a. Impulsivenoisegreaterthan140dBPrequireshearingprotection.b. PertheArmyHearingProgramandtheNavyHearingConservationProgramGuidance

exposuretolevelsabove165dBPrequiresdoublehearingprotectionunlessthesingleprotectioncanbedemonstratedtoreduceat-earlevelstobelow140dBP.

c. FortheAirForce,contactthelocalbioenvironmentalunitorESOHCenterforassistanceinselectingHPDsforimpulsivenoise.

4. Hearing Critical Tasks a. Soundlocalization,whichisdefinedastheabilitytodeterminetheapparentdirection

and/ordistanceofasoundsource,asmeasuredbythetimeittakestofixateonthesource.NOTE:Atthistime,wehavenotestablishedthepointatwhichittakestoomuchtimetoperformamilitarytask.

i. Theposterdepictssoundlocalizationasspatialawareness.b. SpeechIntelligibilityreflectstheabilitytounderstandtransmittedwords.Whenthistask

isimportant,itmayrequirethespeechbeelectronicallytransmittedtobypassthe


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attenuationofthehearingprotectororuseoflevel-dependenthearingprotectorsthatselectivelysuppressunwantedsounds.

5. Wearability a. Includeswhetheradevicecanbewornwithoutinterferingwithotherrequired

equipmentsuchasbattlehelmetand/oreyeprotection.b. Wearerfindsitcomfortablewhenworn.Comfortmaydependonhowlongtheproduct

hastobewornandtheenvironmentinwhichtheproductisused(suchasambienttemperature).

B. Determining Hazardous Noise Requirements TheServicesusenoisesurveysconductedbyoccupationalsafetyandhealthprofessionals,

occupationalaudiologists,industrialhygienists,andbioenvironmentalengineerstodeterminelocationsandequipmentthatarenoisehazardous.Noisesurveysreportsoundpressurelevels(SPLs)andcharacterizethesoundsourceaseithercontinuousorimpulsivenoise.HPDsshouldbeselectedtoprovidetheadequateprotectionagainsttheidentifiednoisehazard.

C. Determining Spatial Awareness Needs Spatialawarenessistheabilitytoaccuratelylocatetheoriginofadetectedsoundinanydirection.Theconceptisillustratedbythequestions‘CanIhearthesound?’and‘CanIdeterminethedirectionofthesound?’Inthemilitary,theabilitytoanswerthesequestionsisimportanttomanyjobsandmissionsandcertainhearingprotectioncaninterferewiththesecapabilities.Jobsthatrequirelocalizationincludedismountedoperations,specialoperations,andforceprotection.Byunderstandingtheperformanceofdevicesandtheimpactontheuser’sabilitytolocatesounds,warfighterscanselectadevicethatwillhaveminimalimpactonspatialawarenesswhileprotectingfromhazardousnoise.

5.0 Conclusion Theinformationprovidedinthisguideistoassistaudiologists,industrial

hygienists/bioenvironmentalengineers,andsafetyprofessionalsinselectingpassivehearingprotectiondevices.QuestionsontheinformationinthisguideorhowtouseitshouldbeaddressedtotheServicePublicHealthCommands/Centers,theESOHServiceCenterortotheDoDHearingCenterofExcellence(https://hearing.health.mil/).


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References

1.Gallagher,H.L.,McKinley,R.L.,Theis,M.A.,Swayne,B.J.,Thompson,E.R.PerformanceAssessmentofPassiveHearingProtectionDevices.AFRL-RH-WR-TR-2014-0148,October2014.

2.DepartmentofDefenseDesignCriteriaStandardNoiseLimits,MIL-STD-1474E,dtd15APR2016.

3.DepartmentofDefenseInstruction6055.12,HearingConservationProgram,dtd3DEC2010.

4.DepartmentoftheArmy.Pamphlet40-501.ArmyHearingProgram.2015.

5.ChiefofNavalOperationsInstruction5100.23GNavyOccupationalSafetyandHealthAshore,dtd21JUL2011.

6.BureauofMedicineandSurgeryNote6260,RevisedInterimNavyMedicineHearingConservationProgramGuidance,dtd24APR2014.

7.AirForceInstruction48-127.OccupationalNoiseandHearingConservationProgram,dtd26FEB2016.


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Annex A. Acronyms ANSI–AmericanNationalStandardsInstitute

ASA–AcousticalSocietyofAmerica

AFRL–AirForceResearchLaboratory

dB–decibel

dBA–decibelA-weighted

dBP–decibelPeak(measuredunweightedorusingtheC-weightedscale)

DoDI–DepartmentofDefenseinstruction

EPA–EnvironmentalProtectionAgency

ESOH–AirForceEnvironment,SafetyandOccupationalHealthOffice

HPD–hearingprotectivedevice

NRR–noisereductionrating

NRSA–noisereductionstatisticA-weighting

SPL–soundpressurelevel

TWA–timeweightedaverage


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Acknowledgements

ThisguidebookwasauthoredbyamultidisciplinaryteamfromtheDoDHearingCenterofExcellence,U.S.Army,U.S.Navy,U.S.AirForceandU.S.MarineCorps.TechnicalcontentwasprovidedbytheAirForceResearchLaboratory,ArmyResearchLaboratory,U.S.ArmyAeromedicalResearchLaboratory,NavalSubmarineMedicalResearchLaboratoryandCaptainWilliamJ.Murphy,Ph.D.fromtheNationalInstituteofOccupationalSafetyandHealth.Specialappreciationisgiventothefollowingindividualswhoprovidedguidance,feedback,orcommentstothedocument(listedinalphabeticalorder):

• WilliamAhroon• KariBuchanan• JeremyFederman• HilaryGallagher• MajorShannonHunt• CommanderPaulaJohnston• CharlesJokel• MajorElizabethMcKenna• RichardMcKinley• LieutenantColonelJohnMerkley• CaptainWilliamMurphy• LieutenantColonelMartinRobinette• AngeliqueScharine• BrianSimpson• EarlStefanson• EricThompson• RobertWilliams• KurtYankaskas

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