ASTM_C_423_-_17.pdf

Designation:C42317Standard Test Method forSound Absorption and Sound Absorption Coefficients bythe Reverberation Room Method1This standard is issued under the fixed designation C423;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method covers the measurement of soundabsorption in a reverberation room by measuring decay rate.Procedures for measuring the absorption of a room,theabsorption of an object,such as an office screen,and the soundabsorption coefficients of a specimen of sound absorptivematerial,such as acoustical ceiling tile,are described.1.2 Field MeasurementsAlthough this test method coverslaboratory measurements,the test method described in 4.1 canbe used for making field measurements of the absorption ofrooms(see also 5.5).A method to measure the absorption ofrooms in the field is described in Test Method E2235.1.3 This test method includes information on laboratoryaccreditation(see Annex A1),asymmetrical screens(see An-nex A2),and reverberation room qualification(see Annex A3).1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2C634 Terminology Relating to Building and EnvironmentalAcousticsE795 Practices for Mounting Test Specimens During SoundAbsorption TestsE2235 Test Method for Determination of Decay Rates forUse in Sound Insulation Test Methods2.2 ANSI Standards:S1.6 Preferred Frequencies,Frequency Levels,and BandNumbers for Acoustical Measurements3S1.11 Specification for Octave-Band and Fractional-Octave-Band Analog and Digital Filters3S1.26 Method for the Calculation of the Absorption ofSound by the Atmosphere3S1.43 Specifications for Integrating-Averaging Sound LevelMeters32.3 IEC StandardsIEC 61672 ElectroacousticsSound Level MetersPart 1:Specifications32.4 ASTM Adjuncts:Historical Applications Note on Sound Absorber43.Terminology3.1 Except as noted in 3.3,the terms and symbols used inthis test method are defined in Terminology C634.The follow-ing definition is not currently included in Terminology C634:3.1.1 sound absorption average,SAAa single numberrating,the average,rounded off to the nearest 0.01,of thesound absorption coefficients of a material for the twelveone-third octave bands from 200 through 2500 Hz,inclusive,measured according to this test method.3.1.1.1 DiscussionThe sound absorption coefficients shallbe rounded off to the nearest 0.01 before averaging.If theunrounded average is an exact midpoint,round to the nexthigher multiple of 0.01.For example,report 0.625 as 0.63.3.2 In previous versions of this test method a single numberrating,called the noise reduction coefficient(NRC),wasdefined as follows: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 Jan.15,2017.Published February 2017.Originallyapproved in 1958.Last previous edition approved 2009 as C423 09a.DOI:10.1520/C0423-17.2For 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.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.4A drawing of this specimen is available at a nominal charge from ASTMInternational Headquarters.Order Adjunct No.ADJC0423.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 9Round the average of the sound absorption coefficientsfor 250,500,1000,and 2000 Hz to the nearest multipleof 0.05.If the unrounded average is an exact midpoint,round to the next higher multiple of 0.05.For example,0.625 and 0.675 would be reported as 0.65 and 0.70,respectively.9The noise reduction coefficient shall be reported in order toprovide comparison with values reported in the past(see12.1.3).3.3 Definition of Term Specific