ASTM E1050-08
(Test Method)Standard Test Method for Impedance and Absorption of Acoustical Materials Using A Tube, Two Microphones and A Digital Frequency Analysis System
Standard Test Method for Impedance and Absorption of Acoustical Materials Using A Tube, Two Microphones and A Digital Frequency Analysis System
SIGNIFICANCE AND USE
This test method can be applied to measure sound absorption coefficients of absorptive materials at normal incidence, that is, 0°. It also can be used to determine specific impedance and admittance ratios. The properties measured with this test method are useful in basic research and product development of sound absorptive materials.
Normal incidence sound absorption coefficients can be quite useful in certain situations where the material is placed within a small acoustical cavity close to a sound source, for example a closely-fitted machine enclosure.
This test method allows one to compare relative values of sound absorption when it is impractical to procure large samples for accurate random-incidence measurements in a reverberation room. Estimates of the random incidence absorption coefficients can be obtained from normal impedance data for locally-reacting materials (2).
Note 2—The classification, “locally-reacting” includes fibrous materials having high internal losses. Formulas have been developed for converting sound absorption properties from normal incidence to random incidence, for both locally-reacting and bulk-reacing materials (3).
Measurements described in this test method can be made with high precision, but these measurements may be misleading. Uncertainties of greater magnitude than those from the measurements may occur from other sources. Care should be exercised to sample nonuniform materials adequately (see 11.1).
SCOPE
1.1 This test method covers the use of an impedance tube, two microphone locations, and a digital frequency analysis system for the determination of normal incidence sound absorption coefficients and normal specific acoustic impedance ratios of materials.
1.2 Laboratory Accreditation—A procedure for accrediting a laboratory for performing this test method is given in Annex A1.
1.3 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the use of this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E1050 – 08
Standard Test Method for
Impedance and Absorption of Acoustical Materials Using A
Tube, Two Microphones and A Digital Frequency Analysis
1
System
This standard is issued under the fixed designation E1050; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
4
1. Scope 2: Transfer-Function Method
1.1 This test method covers the use of an impedance tube,
3. Terminology
two microphone locations, and a digital frequency analysis
3.1 Definitions—The acoustical terminology used in this
system for the determination of normal incidence sound
test method is intended to be consistent with the definitions in
absorption coefficients and normal specific acoustic impedance
Terminology C634.
ratios of materials.
1.2 Laboratory Accreditation—A procedure for accrediting
NOTE 1—Historical literature regarding the measurement of normal
a laboratory for performing this test method is given inAnnex incidence absorption coefficients referred to “transfer function” measure-
ments; however, the term arises from Laplace transform theory and is not
A1.
strictly rigorous when the initial conditions have a non-zero value. The
1.3 This standard does not purport to address the safety
term “frequency response function” arises from more general Fourier
concerns, if any, associated with its use. It is the responsibility
5
transform theory (1). This test method shall retain the use of the former
of the use of this standard to consult and establish appropriate
term although not technically correct. Users should be aware that modern
safety and health practices and determine the applicability of
FFT analyzers may employ the latter terminology.
regulatory limitations prior to use.
3.2 Symbols: The following symbols are used in Section 8
(Procedure):
2. Referenced Documents
3.2.1 brc—normal specific acoustics susceptance ratio.
2
2.1 ASTM Standards:
3.2.2 c—speed of sound, m/s.
C384 Test Method for Impedance andAbsorption ofAcous-
3.2.3 grc—normal specific acoustic conductance ratio.
tical Materials by Impedance Tube Method
3.2.4 G ,G —auto power spectra of the acoustic pressure
11 22
C634 Terminology Relating to Building and Environmental
signal at microphone locations 1 and 2, respectively.
Acoustics
3.2.5 G —cross power spectrum of the acoustic pressure
12
E548 Guide for General Criteria Used for Evaluating Labo-
signals at microphones locations 1 and 2.
3
ratory Competence
3.2.6 H—transfer function of the two microphone signals
2.2 ISO Standards:
corrected for microphone response mismatch.
ISO 10534-1 Acoustics—Determination of Sound Absorp-
¯
3.2.7 H—measured transfer function of the two micro-
tion Coefficient and Impedance or Admittance—Part 1:
phone signals.
4
Impedance Tube Method
I II
3.2.8 H,H —calibration transfer functions for the micro-
ISO 10534–2 Acoustics—Determination of SoundAbsorp-
phones in the standard and switched configurations, respec-
tionCoefficientandImpedanceinImpedanceTubes—Part
tively.
¯
3.2.9 H —complex microphone calibration factor.
c
3.2.10 j—equals –1.
1 =
ThistestmethodisunderthejurisdictionofASTMCommitteeE33onBuilding
-1
3.2.11 k—equal 2pf/c; wave number, m .
and Environmental Acoustics and is the direct responsibility of Subcommittee
E33.01 on Sound Absorption.
3.2.11.1 Discussion—In general the wave number is com-
Current edition approved Jan. 15, 2008. Published February 2008. Originally
plex where k = k8-jk9.k8 is the real component, 2pf/c and k9
approved in 1985. Last previous edition approved in 2007 as E1050 - 07. DOI:
is the imaginary component of the wave number, also referred
10.1520/E1050-08.
-1
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or to as the attenuation constant, Nepers-m .
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
3.2.12 l—distance from the test sample to the centre of the
Standards volume information, refer to the standard’s Document Summary page on
nearest microphone, m.
the ASTM website.
3
Withdrawn. The last approved version of this historical standard is referenced
on www.astm.org.
4 5
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St., The boldface numbers in parentheses refer to the list of references at the end of
4th Floor, New York, NY 10036, http://www.ansi.org. this test method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
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E1050 – 08
3.2.13 r/rc—normal specific acoustic resistance ratio. within a small acoustical cavity close to a sound source
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:E1050–07 Designation: E 1050 – 08
Standard Test Method for
Impedance and Absorption of Acoustical Materials Using A
Tube, Two Microphones and A Digital Frequency Analysis
1
System
This standard is issued under the fixed designation E 1050; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the use of an impedance tube, two microphone locations, and a digital frequency analysis system
forthedeterminationofnormalincidencesoundabsorptioncoefficientsandnormalspecificacousticimpedanceratiosofmaterials.
1.2 Laboratory Accreditation—Aprocedure for accrediting a laboratory for performing this test method is given inAnnexA1.
1.3 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the
use of this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
C 384Test Method for Impedance and Absorption of Acoustical Materials by Impedance Tube Method Test Method for
Nondestructive Measurement of Dry Film Thickness of Nonconductive Coatings Applied to a Nonferrous Metal Base
C 634Terminology Relating to Building and Environmental Acoustics Test Method for Nondestructive Measurement of Dry
Film Thickness of Nonconductive Coatings Applied to a Nonferrous Metal Base
E 548Guide for General Criteria Used for Evaluating Laboratory Competence Test Method for Nondestructive Measurement
of Dry Film Thickness of Nonconductive Coatings Applied to a Nonferrous Metal Base
2.2 ISO Standards:
ISO 10534-1 Acoustics—Determination of Sound Absorption Coefficient and Impedance or Admittance—Part 1: Impedance
3
Tube Method
ISO 10534–2 Acoustics—Determination of Sound Absorption Coefficient and Impedance in Impedance Tubes—Part 2:
3
Transfer-Function Method
3. Terminology
3.1 Definitions— The acoustical terminology used in this test method is intended to be consistent with the definitions in
Terminology C 634.
NOTE 1—Historical literature regarding the measurement of normal incidence absorption coefficients referred to “transfer function” measurements;
however,thetermarisesfromLaplacetransformtheoryandisnotstrictlyrigorouswhentheinitialconditionshaveanon-zerovalue.Theterm“frequency
4
responsefunction”arisesfrommoregeneralFouriertransformtheory(1). Thistestmethodshallretaintheuseoftheformertermalthoughnottechnically
correct. Users should be aware that modern FFT analyzers may employ the latter terminology.
3.2 Symbols: The following symbols are used in Section 8 (Procedure):
3.2.1 brc—normal specific acoustics susceptance ratio.
3.2.2 c—speed of sound, m/s.
3.2.3 grc—normal specific acoustic conductance ratio.
1
This test method is under the jurisdiction of ASTM Committee E33 on Building and Environmental Acoustics and is the direct responsibility of Subcommittee E33.01
on Sound Absorption.
Current edition approved Dec. 1, 2007. Published January 2008. Originally approved in 1985. Last previous edition approved in 2006 as E1050-98 (2006).
Current edition approved Jan. 15, 2008. Published February 2008. Originally approved in 1985. Last previous edition approved in 2007 as E 1050 - 07.
2
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
The boldface numbers in parentheses refer to the list of references at the end of this test method.
3
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
4
Supporting data is available from ASTM Headquarters. Request RR:E-33-1006.
4
The boldface numbers in parentheses refer to the list of references at the end of this test method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
---------------------- Page: 1 ----------------------
E1050–08
3.2.4 G ,G —auto power spectra of the acoustic pressure signal at microphone locat
...
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