ASTM C423-23
(Test Method)Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method
Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method
SIGNIFICANCE AND USE
5.1 Measurement of the sound absorption of a room is part of the procedure for other acoustical measurements, such as determining the sound power level of a noise source or the sound transmission loss of a partition. It is also used in certain calculations such as predicting the sound pressure level in a room when the sound power level of a noise source in the room is known.
5.2 The sound absorption coefficient of a surface is a property of the material composing the surface. It is ideally defined as the fraction of the randomly incident sound power absorbed by the surface, but in this test method it is operationally defined in 4.2. The relationship between the theoretically defined and the operationally measured coefficients is under continuing study.
5.3 Diffraction effects4 usually cause the apparent area of a specimen to be greater than its geometrical area, thereby increasing the coefficients measured according to this test method. When the test specimen is highly absorptive, these values may exceed unity.
5.4 The coefficients measured by this test method should be used with caution because not only are the areas encountered in practical usage usually larger than the test specimen, but also the sound field is rarely diffuse. In the laboratory, measurements must be made under reproducible conditions, but in practical usage the conditions that determine the effective absorption are often unpredictable. Regardless of the differences and the necessity for judgment, coefficients measured by this test method have been used successfully by architects and consultants in the acoustical design of architectural spaces.
5.5 Field Measurements—When sound absorption measurements are made in a building in which the size and shape of the room are not under the operator's control, the approximation to a diffuse sound field is not likely to be very close. This matter should be considered when assessing the accuracy of measurements made under field conditions. (See Te...
SCOPE
1.1 This test method covers the measurement of sound absorption in a reverberation room by measuring decay rate. Procedures for measuring the absorption of a room, the absorption of an object, such as an office screen, and the sound absorption coefficients of a specimen of sound absorptive material, such as acoustical ceiling tile, are described.
1.2 Field Measurements—Although this test method covers laboratory measurements, the test method described in 4.1 can be used for making field measurements of the absorption of rooms (see also 5.5). A method to measure the absorption of rooms in the field is described in Test Method E2235.
1.3 This test method includes information on laboratory accreditation (see Annex A1), asymmetrical screens (see Annex A2), and reverberation room qualification (see Annex A3).
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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.
1.6 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.
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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: C423 − 23
Standard Test Method for
Sound Absorption and Sound Absorption Coefficients by
1
the Reverberation Room Method
This standard is issued under the fixed designation C423; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 2. Referenced Documents
2
1.1 This test method covers the measurement of sound 2.1 ASTM Standards:
absorption in a reverberation room by measuring decay rate. C634 Terminology Relating to Building and Environmental
Procedures for measuring the absorption of a room, the Acoustics
absorption of an object, such as an office screen, and the sound E795 Practices for Mounting Test Specimens During Sound
absorption coefficients of a specimen of sound absorptive Absorption Tests
material, such as acoustical ceiling tile, are described. E2235 Test Method for Determination of Decay Rates for
Use in Sound Insulation Test Methods
1.2 Field Measurements—Although this test method covers
2.2 ANSI Standards:
laboratory measurements, the test method described in 4.1 can
S1.6 Preferred Frequencies, Frequency Levels, and Band
be used for making field measurements of the absorption of
3
Numbers for Acoustical Measurements
rooms (see also 5.5). A method to measure the absorption of
S1.11 Specification for Octave-Band and Fractional-Octave-
rooms in the field is described in Test Method E2235.
3
Band Analog and Digital Filters
1.3 This test method includes information on laboratory
S1.26 Method for the Calculation of the Absorption of
accreditation (see Annex A1), asymmetrical screens (see An- 3
Sound by the Atmosphere
nex A2), and reverberation room qualification (see Annex A3).
S1.43 Specifications for Integrating-Averaging Sound Level
3
1.4 The values stated in SI units are to be regarded as Meters
standard. No other units of measurement are included in this
2.3 IEC Standards
standard. IEC 61672 Electroacoustics–Sound Level Meters–Part 1:
3
Specifications
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
3.1 Except as noted in 3.3, the terms and symbols used in
priate safety, health, and environmental practices and deter-
this test method are defined in Terminology C634. The follow-
mine the applicability of regulatory limitations prior to use.
ing definition is not currently included in Terminology C634:
1.6 This international standard was developed in accor-
3.1.1 sound absorption average, SAA—a single number
dance with internationally recognized principles on standard-
rating, the average, rounded off to the nearest 0.01, of the
ization established in the Decision on Principles for the
sound absorption coefficients of a material for the twelve
Development of International Standards, Guides and Recom-
one-third octave bands from 200 through 2500 Hz, inclusive,
mendations issued by the World Trade Organization Technical
measured according to this test method.
Barriers to Trade (TBT) Committee.
1 2
This test method is under the jurisdiction of ASTM Committee E33 on Building For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and Environmental Acoustics and is the direct responsibility of Subcommittee contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
E33.01 on Sound Absorption. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved April 15, 2023. Published May 2023. Originally the ASTM website.
3
approved in 1958. Last previous edition approved in 2022 as C423 – 22. DOI: Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/C0423-23. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
C423 − 23
3.1.1.1 Discussion—The sound absorption coefficients shall 4.3 Measurement of the Sound Absorption of an Object Such
be rounded off to the nearest 0.01 before averaging. If the as an Offıce Screen, a Theater Chair, or a Space Absorber—
unrounded average is an exact midpoint, round to the next The absorption of the reverberation room is measured as
higher multiple of 0.01. For example, report 0.625 as 0.63. outlin
...
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: C423 − 22 C423 − 23
Standard Test Method for
Sound Absorption and Sound Absorption Coefficients by
1
the Reverberation Room Method
This standard is issued under the fixed designation C423; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 This test method covers the measurement of sound absorption in a reverberation room by measuring decay rate. Procedures
for measuring the absorption of a room, the absorption of an object, such as an office screen, and the sound absorption coefficients
of a specimen of sound absorptive material, such as acoustical ceiling tile, are described.
1.2 Field Measurements—Although this test method covers laboratory measurements, the test method described in 4.1 can be used
for making field measurements of the absorption of rooms (see also 5.5). A method to measure the absorption of rooms in the field
is described in Test Method E2235.
1.3 This test method includes information on laboratory accreditation (see Annex A1), asymmetrical screens (see Annex A2), and
reverberation room qualification (see Annex A3).
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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.
1.6 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:
C634 Terminology Relating to Building and Environmental Acoustics
E795 Practices for Mounting Test Specimens During Sound Absorption Tests
E2235 Test Method for Determination of Decay Rates for Use in Sound Insulation Test Methods
2.2 ANSI Standards:
3
S1.6 Preferred Frequencies, Frequency Levels, and Band Numbers for Acoustical Measurements
3
S1.11 Specification for Octave-Band and Fractional-Octave-Band Analog and Digital Filters
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 Feb. 1, 2022April 15, 2023. Published March 2022May 2023. Originally approved in 1958. Last previous edition approved in 20172022 as
C423 – 17.C423 – 22. DOI: 10.1520/C0423-22.10.1520/C0423-23.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM 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
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
C423 − 23
3
S1.26 Method for the Calculation of the Absorption of Sound by the Atmosphere
3
S1.43 Specifications for Integrating-Averaging Sound Level Meters
2.3 IEC Standards
3
IEC 61672 Electroacoustics–Sound Level Meters–Part 1: Specifications
3. Terminology
3.1 Except as noted in 3.3, the terms and symbols used in this test method are defined in Terminology C634. The following
definition is not currently included in Terminology C634:
3.1.1 sound absorption average, SAA—a single number rating, the average, rounded off to the nearest 0.01, of the sound absorption
coefficients of a material for the twelve one-third octave bands from 200 through 2500 Hz, inclusive, measured according to this
test method.
3.1.1.1 Discussion—The sound absorption coefficients shall be rounded off to the nearest 0.01 before averaging. If the unrounded
average is an exact midpoint, round to the next higher multiple of 0.01. For example, report 0.625 as 0.63.
3.2 In pr
...
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