ASTM E1050-19

Standard Test Method for Impedance and Absorption of Acoustical Materials Using a Tube, Two Microphones and a Digital Frequency Analysis System

SIGNIFICANCE AND USE
5.1 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.  
5.2 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.  
5.3 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).  
5.4 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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Sep-2019
• Technical Committee: E33 - Building and Environmental Acoustics
• Drafting Committee: E33.01 - Sound Absorption

Relations

• Referred By: ASTM E1179-13(2019) - Standard Specification for Sound Sources Used for Testing Open Office Components and Systems
• Effective Date: 01-Oct-2019
• Referred By: ASTM E2611-19 - Standard Test Method for Normal Incidence Determination of Porous Material Acoustical Properties Based on the Transfer Matrix Method
• Effective Date: 01-Oct-2019
• Referred By: ASTM E2813-18 - Standard Practice for Building Enclosure Commissioning
• Effective Date: 01-Oct-2019
• Referred By: ASTM C634-22 - Standard Terminology Relating to Building and Environmental Acoustics
• Effective Date: 01-Oct-2019

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1050 − 19
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.
1. Scope E548 Guide for General Criteria Used for Evaluating Labo-
3
ratory Competence (Withdrawn 2002)
1.1 This test method covers the use of an impedance tube,
2.2 ISO Standards:
two microphone locations, and a digital frequency analysis
ISO 10534-1 Acoustics—Determination of Sound Absorp-
system for the determination of normal incidence sound
tion Coefficient and Impedance or Admittance—Part 1:
absorption coefficients and normal specific acoustic impedance
4
Impedance Tube Method
ratios of materials.
ISO 10534–2 Acoustics—Determination of Sound Absorp-
1.2 Laboratory Accreditation—A procedure for accrediting
tionCoefficientandImpedanceinImpedanceTubes—Part
a laboratory for performing this test method is given in Annex
4
2: Transfer-Function Method
A1.
4
2.3 ANSI Standards:
1.3 The values stated in SI units are to be regarded as
ANSI/ASAS1.11 Octave-Band and Fractional-Octave-Band
standard. No other units of measurement are included in this
Analog and Digital Filters
standard.
3. Terminology
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3.1 Definitions—Theacousticalterminologyusedinthistest
responsibility of the user of this standard to establish appro-
method is intended to be consistent with the definitions in
priate safety, health, and environmental practices and deter-
Terminology C634.
mine the applicability of regulatory limitations prior to use.
NOTE 1—Historical literature regarding the measurement of normal
1.5 This international standard was developed in accor-
incidence absorption coefficients referred to “transfer function” measure-
dance with internationally recognized principles on standard-
ments; however, the term arises from Laplace transform theory and is not
ization established in the Decision on Principles for the strictly rigorous when the initial conditions have a non-zero value. The
term “frequency response function” arises from more general Fourier
Development of International Standards, Guides and Recom-
5
transform theory (1). This test method shall retain the use of the former
mendations issued by the World Trade Organization Technical
term although not technically correct. Users should be aware that modern
Barriers to Trade (TBT) Committee.
FFT analyzers may employ the latter terminology.
3.2 Symbols: The following symbols are used in Section 8
2. Referenced Documents
(Procedure):
2
2.1 ASTM Standards:
3.2.1 bρc—normal specific acoustics susceptance ratio.
C384 Test Method for Impedance andAbsorption ofAcous-
3.2.2 c—speed of sound, m/s.
tical Materials by Impedance Tube Method
3.2.3 gρc—normal specific acoustic conductance ratio.
C634 Terminology Relating to Building and Environmental
Acoustics
3.2.4 G ,G —auto power spectra of the acoustic pressure
11 22
signal at microphone locations 1 and 2, respectively.
3.2.5 G —cross power spectrum of the acoustic pressure
12
1
ThistestmethodisunderthejurisdictionofASTMCommitteeE33onBuilding
signals at microphones locations 1 and 2.
and Environmental Acoustics and is the direct responsibility of Subcommittee
E33.01 on Sound Absorption.
Current edition approved Oct. 1, 2019. Published November 2019. Originally
3
approved in 1985. Last previous edition approved in 2012 as E1050 – 12. DOI: The last approved version of this historical standard is referenced on
10.1520/E1050-19. www.astm.org.
2 4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM 4th Floor, New York, NY 10036, http://www.ansi.org.
5
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers in parentheses refer to the list of references at the end of
the ASTM website. this test method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
E1050 − 19
3.2.6 H—transfer function of the two microphone signals incidence absorption coefficients for the a
...

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 − 12 E1050 − 19
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.
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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the useuser of this standard to consult and establish appropriate safety safety, health, and healthenvironmental practices and
determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
C384 Test Method for Impedance and Absorption of Acoustical Materials by Impedance Tube Method
C634 Terminology Relating to Building and Environmental Acoustics
3
E548 Guide for General Criteria Used for Evaluating Laboratory Competence (Withdrawn 2002)
2.2 ISO Standards:
ISO 10534-1 Acoustics—Determination of Sound Absorption Coefficient and Impedance or Admittance—Part 1: Impedance
4
Tube Method
ISO 10534–2 Acoustics—Determination of Sound Absorption Coefficient and Impedance in Impedance Tubes—Part 2:
4
Transfer-Function Method
4
2.3 ANSI Standards:
ANSI/ASA S1.11 Octave-Band and Fractional-Octave-Band Analog and Digital Filters
3. Terminology
3.1 Definitions—The acoustical terminology used in this test method is intended to be consistent with the definitions in
Terminology C634.
NOTE 1—Historical literature regarding the measurement of normal incidence absorption coefficients referred to “transfer function” measurements;
however, the term arises from Laplace transform theory and is not strictly rigorous when the initial conditions have a non-zero value. The term “frequency
5
response function” arises from more general Fourier transform theory (1). This test method shall retain the use of the former term although not technically
correct. Users should be aware that modern FFT analyzers may employ the latter terminology.
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 April 1, 2012Oct. 1, 2019. Published July 2012November 2019. Originally approved in 1985. Last previous edition approved in 20102012 as
E1050 - 10.E1050 – 12. DOI: 10.1520/E1050-12.10.1520/E1050-19.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
The last approved version of this historical standard is referenced on www.astm.org.
4
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
5
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 − 19
3.2 Symbols: The following symbols are used in Section 8 (Procedure):
3.2.1 bρc—normal specific acoustics susceptance ratio.
3.2.2 c—speed of sound, m/s.
3.2.3 gρc—normal specific acoustic conductance ratio.
3.2.4 G , G —auto power spectra of the acoustic pressure signal at microphone locations 1 and
...