ASTM_E_1050_-_12.pdf

Designation:E105012Standard Test Method forImpedance and Absorption of Acoustical Materials Using aTube,Two Microphones and a Digital Frequency AnalysisSystem1This standard is issued under the fixed designation E1050;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the use of an impedance tube,two microphone locations,and a digital frequency analysissystem for the determination of normal incidence soundabsorption coefficients and normal specific acoustic impedanceratios of materials.1.2 Laboratory AccreditationA procedure for accreditinga laboratory for performing this test method is given in AnnexA1.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 This standard does not purport to address the safetyconcerns,if any,associated with its use.It is the responsibilityof the use of this standard to consult and establish appropriatesafety and health practices and determine the applicability ofregulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2C384 Test Method for Impedance and Absorption of Acous-tical Materials by Impedance Tube MethodC634 Terminology Relating to Building and EnvironmentalAcousticsE548 Guide for General Criteria Used for Evaluating Labo-ratory Competence(Withdrawn 2002)32.2 ISO Standards:ISO 10534-1 AcousticsDetermination of Sound Absorp-tion Coefficient and Impedance or AdmittancePart 1:Impedance Tube Method4ISO 105342 AcousticsDetermination of Sound Absorp-tion Coefficient and Impedance in Impedance TubesPart2:Transfer-Function Method42.3 ANSI Standards:4ANSI/ASA S1.11 Octave-Band and Fractional-Octave-BandAnalog and Digital Filters3.Terminology3.1 DefinitionsThe acoustical terminology used in this testmethod is intended to be consistent with the definitions inTerminology C634.NOTE1Historical literature regarding the measurement of normalincidence absorption coefficients referred to“transfer function”measure-ments;however,the term arises from Laplace transform theory and is notstrictly rigorous when the initial conditions have a non-zero value.Theterm“frequency response function”arises from more general Fouriertransform theory(1).5This test method shall retain the use of the formerterm although not technically correct.Users should be aware that modernFFT analyzers may employ the latter terminology.3.2 Symbols:The following symbols are used in Section 8(Procedure):3.2.1 bcnormal specific acoustics susceptance ratio.3.2.2 cspeed of sound,m/s.3.2.3 gcnormal specific acoustic conductance ratio.3.2.4 G11,G22auto power spectra of the acoustic pressuresignal at microphone locations 1 and 2,respectively.3.2.5 G12cross power spectrum of the acoustic pressuresignals at microphones locations 1 and 2.3.2.6 Htransfer function of the two microphone signalscorrected for microphone response mismatch.3.2.7 Hmeasured transfer function of the two microphonesignals.3.2.8 HI,HIIcalibration transfer functions for the micro-phones in the standard and switched configurations,respec-tively.1This test method is under the jurisdiction ofASTM Committee E33 on Buildingand Environmental Acoustics and is the direct responsibility of SubcommitteeE33.01 on Sound Absorption.Current edition approved April 1,2012.Published July 2012.Originallyapproved in 1985.Last previous edition approved in 2010 as E1050-10.DOI:10.1520/E1050-12.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.5The boldface numbers in parentheses refer to the list of references at the end ofthis test method.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.9 Hccomplex microphone calibration factor.3.2.10 jequals=21.3.2.11 kequal 2f/c;wave number,m-1.3.2.11.1 DiscussionIn general the wave number is com-plex where k=k-jk.k is the real component,2f/c and kis the imaginary component of the wave number,also referredto as the attenuation constant,Nepers-m-1.3.2.12 ldistance from the test sample to the centre of thenearest microphone,m.3.2.13 r/cnormal specific acoustic resistance ratio.3.2.14 Rcomplex acoustic reflection coefficient.3.2.15 scentre-to-center spacing between microphones,m.3.2.16 x/cnormal specific acoustic reactance ratio.3.2.17 ycnormal specific acoustic admittance ration.3.2.18 z/cnormal specific acoustic impedance ratio.3.2.19 a