bn0221Imp_of_canal

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1、ImpedanceofRealandArtificialEarsPARTI:InvestigationsofaNewInsertEarphoneCoupler3(SmallArtificialEar)Authors:PerV.BriielErlingFrederiksenHilmerMathiasenGunnarRasmussenErikSighPARTII:ImpedanceMeasurementsofVolumes30Authors:PerV.BruelViggoTarnowPARTIII:ApplicationsofSmallArtificialEars33Aut

2、hors:PerV.BruelErikSighPARTIForhelpingthehearingaidindustryandtheusersofhearingaids,IEChasdescribedinR1261>1961anartificialearcalledtheIEC2cm3Coupler,whichcouldbeusedforevaluationofsensitivityandfrequencyresponseofhearingaidearphones.AsketchofthecouplerisshowninFig.1,topleft.Fig.1.Cross-

3、sectionanddimensionsoftheIEC2cm3coupler,theZwislocki,Diestel-P.T.B.andtheKellercouplerThecouplerconsistsofa2cm3volumewhichshouldsimulatethevolumebetweenthetipoftheearmouldandtheeardrum,includingtheelasticityoftheeardrumandtheinnerpartoftheearcanal.An18mmlongand3mmdiametercylindricalcavit

4、yleadsfromtheearphoneundertesttothevolume.Thiscavitysimulatesthetubularportionofanaverageearmould.3Thewholeeardevicewassuggestedalreadyin1949anddescribedinanASAstandardZ.24.9.Thecouplerinthepresentconfigurationisthereforeratherold,anditisnowknownthatboththeimpedanceandthefrequencyrespons

5、edifferconsiderablyfromthoseofthehumanear.Manyinvestigatorshavelookedintotheproblemofmakinganewcoupler,forexample,Zwislocki2),Diestel3)andKeller4)togetherwithothershavecomeupwithsuggestionsforrevisedversionsofcouplersforinsertearphonesshowninFig.1.Theseattemptswillonlybebrieflytouchedupo

6、nhere.RequirementsBycouplerisnormallyunderstoodadevicewhichconnectstheearphoneundertesttoamicrophoneinsuchawaythattheworkingloadontheearphoneisthesameasiftheearphonewasusedonarealear.Furthermorethecouplershouldbemadeinsuchawaythatthesignalpickedupbythemicrophoneasfunctionoffrequencyisthe

7、sameasthesoundpressureintheearcanalattheeardrum.Ifthesetworequirementscanbefulfilledaccurately,thenthedevicemaybecalledanartificialear,completelyinanalogywiththetermsusedintheIECR3185)whichdescribesanartificialearintendedforcalibrationofsupra-auralearphones.Themostimporta