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1、Designation:E1050?12StardTestMethodfImpedanceAbsptionofAcousticalMaterialsUsingaTubeTwoMicrophonesaDigitalFrequencyAnalysisSystem1ThisstardisissuedunderthefixeddesignationE1050thenumberimmediatelyfollowingthedesignationi

2、ndicatestheyearofiginaladoptioninthecaseofrevisiontheyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperepsilon()indicatesaneditialchangesincethelastrevisionreapproval.1.Scope1.1Thistestmethodc

3、overstheuseofanimpedancetubetwomicrophonelocationsadigitalfrequencyanalysissystemfthedeterminationofnmalincidencesoundabsptioncoefficientsnmalspecificacousticimpedanceratiosofmaterials.1.2LabatyAccreditation—Aprocedurefa

4、ccreditingalabatyfperfmingthistestmethodisgiveninAnnexA1.1.3ThevaluesstatedinSIunitsaretoberegardedasstard.Nootherunitsofmeasurementareincludedinthisstard.1.4Thisstarddoesnotpurpttoaddressthesafetyconcernsifanyassociated

5、withitsuse.Itistheresponsibilityoftheuseofthisstardtoconsultestablishappropriatesafetyhealthpracticesdeterminetheapplicabilityofregulatylimitationspritouse.2.ReferencedDocuments2.1ASTMStards:2C384TestMethodfImpedanceAbsp

6、tionofAcousticalMaterialsbyImpedanceTubeMethodC634TerminologyRelatingtoBuildingEnvironmentalAcousticsE548GuidefGeneralCriteriaUsedfEvaluatingLaboratyCompetence(Withdrawn2002)32.2ISOStards:ISO105341Acoustics—Determination

7、ofSoundAbsptionCoefficientImpedanceAdmittance—Part1:ImpedanceTubeMethod4ISO10534–2Acoustics—DeterminationofSoundAbsptionCoefficientImpedanceinImpedanceTubes—Part2:TransferFunctionMethod42.3ANSIStards:4ANSIASAS1.11OctaveB

8、FractionalOctaveBAnalogDigitalFilters3.Terminology3.1Definitions—TheacousticalterminologyusedinthistestmethodisintendedtobeconsistentwiththedefinitionsinTerminologyC634.NOTE1—Histicalliteratureregardingthemeasurementofnm

9、alincidenceabsptioncoefficientsreferredto“transferfunction”measurementshoweverthetermarisesfromLaplacetransfmtheyisnotstrictlyrigouswhentheinitialconditionshaveanonzerovalue.Theterm“frequencyresponsefunction”arisesfromme

10、generalFouriertransfmthey(1).5Thistestmethodshallretaintheuseofthefmertermalthoughnottechnicallycrect.UsersshouldbeawarethatmodernFFTanalyzersmayemploythelatterterminology.3.2Symbols:ThefollowingsymbolsareusedinSection8(

11、Procedure):3.2.1bρc—nmalspecificacousticssusceptanceratio.3.2.2c—speedofsoundms.3.2.3gρc—nmalspecificacousticconductanceratio.3.2.4G11G22—autopowerspectraoftheacousticpressuresignalatmicrophonelocations12respectively.3.2

12、.5G12—crosspowerspectrumoftheacousticpressuresignalsatmicrophoneslocations12.3.2.6H—transferfunctionofthetwomicrophonesignalscrectedfmicrophoneresponsemismatch.3.2.7H—measuredtransferfunctionofthetwomicrophonesignals.3.2

13、.8HIHII—calibrationtransferfunctionsfthemicrophonesinthestardswitchedconfigurationsrespectively.1ThistestmethodisunderthejurisdictionofASTMCommitteeE33onBuildingEnvironmentalAcousticsisthedirectresponsibilityofSubcommitt

14、eeE33.01onSoundAbsption.CurrenteditionapprovedApril12012.PublishedJuly2012.iginallyapprovedin1985.Lastpreviouseditionapprovedin2010asE105010.DOI:10.1520E105012.2FreferencedASTMstardsvisittheASTMwebsitewww.astm.gcontactAS

15、TMCustomerServiceat.FAnnualBookofASTMStardsvolumeinfmationrefertothestard’sDocumentSummarypageontheASTMwebsite.3Thelastapprovedversionofthishisticalstardisreferencedonwww.astm.g.4AvailablefromAmericanNationalStardsInstit

16、ute(ANSI)25W.43rdSt.4thFloNewYkNY10036:www.ansi.g.5Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendofthistestmethod.Copyright?ASTMInternational100BarrHarbDrivePOBoxC700WestConshohockenPA194282959.UnitedS

17、tates1fl=lowerwkingfrequencyofthetubehertzfu=upperwkingfrequencyofthetubehertz.6.2.2.1Thelowerfrequencylimitdependsonthespacingofthemicrophonestheaccuracyoftheanalysissystem.Itisrecommendedthatthemicrophonespacingexceedo

18、nepercentofthewavelengthcrespondingtothelowerfrequencyofinterest.6.2.2.2Theupperfrequencylimitfuthecrespondingwavelengthλudependsonthediameterofthetubeuponthespeedofsound.6.2.3Diameter—Indertomaintainplanewavepropagation

19、theupperfrequencylimit(4)isdefinedasfollows:fuKcddKcfu(2)where:fu=upperfrequencylimithertzc=speedofsoundinthetubemsd=diameterofthetubemK=0.586.6.2.3.1FrectangulartubesdisdefinedasthelargestsectiondimensionthetubeKisdefin

20、edas0.500.Extremeaspectrationsgreaterthan2:1lessthan1:2shouldbeavoided.Asquarecrosssectionisrecommended.6.2.3.2Itisbesttoconducttheplanewavemeasurementswellwithinthesefrequencylimitsindertoavoidcrossmodesthatoccurathighe

21、rfrequencieswhentheacousticalwavelengthapproachesthesectionaldimensionofthetube.6.2.4Length—Thetubeshouldbesufficientlylongasplanewavesarefullydevelopedbefereachingthemicrophonestestspecimen.Aminimumofthreetubediametersm

22、ustbeallowedbetweensoundsourcethenearestmicrophone.Thesoundsourcemaygeneratenonplanewavesalongwithdesiredplanewaves.Thenonplanewavesusuallywillsubsideatadistanceequivalenttothreetubediametersfromthesource.Ifmeasurementsa

23、reconductedoverawidefrequencyrangeitmaybedesirabletouseatubewhichprovidesmultiplemicrophonespacingstoemployseparatetubes.Theoveralltubelengthalsomustbechosentosatisfytherequirementsof6.4.36.5.36.5.4.6.2.5TubeVenting—Some

24、tubedesignsaresuchthatduringduringinstallationremovalofthetestspecimenlargetemparypressurevariationmaybegenerated.Thismayinducemicrophonediaphragmdeflection.Thepotentialfdamagetoamicrophonediaphragmduetoexcessivedeflecti

25、onmaybereducedincludingapressurereliefopeninginthetube.Thismaybeaccomplishedbydrillingasmallhole1to2mmthroughthewallofthetube.Itisrecommendedtolocatethetubeventnearthesoundsourceawayfrommicrophonelocationstosealtheventdu

26、ringacousticmeasurements.6.3TestSpecimenHolder:6.3.1GeneralFeatures—Thespecimenholdermayeitherbeintegratedwiththeimpedancetubemaybeaseparatedetachableextensionofthetube.Provisionmustbemadefmountingthespecimenwithitsfacei

27、naknownpositionalongthetubeaxisfplacingaheavybackingplatebehindthespecimen.Fsomemeasurementsitmaybedesirabletomaintainanairspaceofknowndimensionsbetweenthespecimenthebackingplate.Onesucharrangementmaybetosimulateasuspend

28、edceilingtile.6.3.2DetachableHolder—Asadetachableunittheholdermustmakeanairtightfitwiththeendofthetubeoppositethesoundsource.Theholdermustconfmwiththeinterishapedimensionsofthemainpartoftheimpedancetube.Theconnectingjoin

29、tmustbefinishedcarefullytheuseofasealantsuchaspetroleumjellysiliconegreaseisrecommendedfsealing.6.3.3IntegralHolder—Ifthesampleholderisinanintegralpartoftheimpedancetubeitisrecommendedtomaketheinstallationsectionofthetub

30、eaccessiblefmountingofthespecimenbyaremovablecover.Thematingsurfacesmustbefinishedcarefullytheuseofasealantisrecommendedfsealing.6.3.4CircularHolder—Fcirculartubesitisrecommendedtomakethespecimenaccessiblefromboththefron

31、tbackendofthesampleholder.Itispossiblethentocheckthepositionflatnessofthefrontsurfacebackposition.Holdersmaybeconstructedfromarigidclearmaterialsuchasacrylictofacilitateinspection.6.3.5RectangularHolder—Withrectangulartu

32、besitisrecommendedtoinstallthespecimenfromthesidemakingitpossibletocheckthefittingthepositionofthespecimeninthetubetocheckthepositionflatnessofthefrontsurface.6.3.6BackingPlate—Thebackingplateofthesampleholdershallberigi

33、dshallbefixedtightlytothetubesinceitservestoprovideasoundreflectiveterminationinmanymeasurements.Ametalplatehavingaminimumthicknessof20mmisrecommended.6.4SoundSource:6.4.1KindPlacement—Thesoundsourcesshouldhaveaunifmpowe

34、rresponseoverthefrequencyrangeofinterest.Itmayeitherbecoaxialwiththemaintubejoinedtothemaintubebymeansofatransitionhavingastraighttaperedexponentialsection(seeFig.1).6.4.2Isolation—Thesoundsourcetransitionshallbesealedis

35、olatedfromthetubetominimizestructurebnesoundexcitationoftheimpedancetube.Ifadirectradiatloudspeakerisutilizeditshallbecontainedinasoundisolatingenclosureindertoavoidairbneflankingtransmissiontothemicrophones(seeFig.1).6.

36、4.3Termination—Resonancesoftheaircolumnintheimpedancetubemayariseifthemechanicalimpedanceoftheloudspeakermembranediaphragmishigh.Inthiscaseitisrecommendedtoapplyapousabsbercoatinglininginsideeithertheimpedancetubenearthe

37、loudspeakerinsidethesoundtransition.Alternativelythelocationsdescribesabovemaybefilledlightlywithalowdensityabsbingmaterial.6.4.4Equalization—Whenanabsptivemediumisplacednearthesoundsourceasdescribedin6.4.3significantsou

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