ASTM C423-02a

Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method

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.
1.2Field Measurements—Although this test method primarily 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 non-standard method to measure the absorption of rooms in the field is described in Appendix X2.
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  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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-Dec-2002
• ICS: 91.120.20 - Acoustics in building. Sound insulation
• Technical Committee: E33 - Building and Environmental Acoustics
• Drafting Committee: E33.01 - Sound Absorption

Relations

• Replaces: ASTM C423-02 - Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method
• Effective Date: 10-Dec-2002
• Replaced By: ASTM C423-02ae1 - Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method
• Effective Date: 10-Dec-2002
• Referred By: ASTM D5456-21e1 - Standard Specification for Evaluation of Structural Composite Lumber Products
• Effective Date: 10-Dec-2002
• Referred By: ASTM C1014-17 - Standard Specification for Spray-Applied Mineral Fiber Thermal and Sound Absorbing Insulation
• Effective Date: 10-Dec-2002
• Referred By: ASTM C842-05(2021) - Standard Specification for Application of Interior Gypsum Plaster
• Effective Date: 10-Dec-2002
• Referred By: ASTM C384-04(2022) - Standard Test Method for Impedance and Absorption of Acoustical Materials by Impedance Tube Method
• Effective Date: 10-Dec-2002
• Referred By: ASTM C1410-17(2023) - Standard Specification for Cellular Melamine Thermal and Sound-Absorbing Insulation
• Effective Date: 10-Dec-2002
• Referred By: ASTM C1482-23 - Standard Specification for Polyimide Flexible Cellular Thermal and Sound Absorbing Insulation
• Effective Date: 10-Dec-2002
• Referred By: ASTM C1685-15(2021) - Standard Specification for Pneumatically Applied High-Temperature Fiber Thermal Insulation for Industrial Applications
• Effective Date: 10-Dec-2002
• Referred By: ASTM C1071-19 - Standard Specification for Fibrous Glass Duct Lining Insulation (Thermal and Sound Absorbing Material)
• Effective Date: 10-Dec-2002
• Referred By: ASTM E2813-18 - Standard Practice for Building Enclosure Commissioning
• Effective Date: 10-Dec-2002
• Referred By: ASTM E1264-23 - Standard Classification for Acoustical Ceiling Products
• Effective Date: 10-Dec-2002
• Referred By: ASTM E2235-04(2020) - Standard Test Method for Determination of Decay Rates for Use in Sound Insulation Test Methods
• Effective Date: 10-Dec-2002
• Referred By: ASTM E1222-22 - Standard Test Method for Laboratory Measurement of the Insertion Loss of Pipe Lagging Systems
• Effective Date: 10-Dec-2002
• Referred By: ASTM C844-15(2021) - Standard Specification for Application of Gypsum Base to Receive<brk/> Gypsum Veneer Plaster
• Effective Date: 10-Dec-2002

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:C423–02a
Standard Test Method for
Sound Absorption and Sound Absorption Coefficients by
1
the Reverberation Room Method
This standard is issued under the fixed designation C 423; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope S1.11 Specification for Octave-Band and Fractional-
4
Octave-Band Analog and Digital Filters
1.1 This test method covers the measurement of sound
S1.26 Method for the Calculation of the Absorption of
absorption in a reverberation room by measuring decay rate.
4
Sound by the Atmosphere
Procedures for measuring the absorption of a room, the
absorption of an object, such as an office screen, and the sound
3. Terminology
absorption coefficients of a specimen of sound absorptive
3.1 Except as noted in 3.3, the terms and symbols used in
material, such as acoustical ceiling tile, are described.
this test method are defined in Terminology C 634. The
1.2 Field Measurements—Although this test method prima-
following definition is not currently included in Terminology
rily covers laboratory measurements, the test method described
C 634:
in 4.1 can be used for making field measurements of the
3.1.1 sound absorption average, SAA—a single number
absorption of rooms (see also 5.5). A non-standard method to
rating, the average, rounded off to the nearest 0.01, of the
measure the absorption of rooms in the field is described in
sound absorption coefficients of a material for the twelve
Appendix X2.
one-third octave bands from 200 through 2500 Hz, inclusive,
1.3 This test method includes information on laboratory
measured according to this test method.
accreditation (see Annex A1), asymmetrical screens (see An-
3.1.1.1 Discussion—The sound absorption coefficients shall
nexA2), and reverberation room qualification (seeAnnexA3).
be rounded off to the nearest 0.01 before averaging. If the
1.4 This standard does not purport to address all of the
unrounded average is an exact midpoint, round to the next
safety concerns, if any, associated with its use. It is the
higher multiple of 0.01. For example, report 0.625 as 0.63.
responsibility of the user of this standard to establish appro-
3.2 In previous versions of this test method a single number
priate safety and health practices and determine the applica-
rating, called the noise reduction coefficient (NRC), was
bility of regulatory limitations prior to use.
defined as follows:
2. Referenced Documents
9Round the average of the sound absorption coefficients
for 250, 500, 1000, and 2000 Hz to the nearest multiple
2.1 ASTM Standards:
of 0.05. If the unrounded average is an exact midpoint,
2
C 634 Terminology Relating to Environmental Acoustics 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.9
E 548 Practice for Generic Criteria for Use in Evaluation of
3
Testing and Inspection Agencies
The noise reduction coefficient shall be reported in order to
E 795 Practices for Mounting Test Specimens During
provide comparison with values reported in the past see
2
Sound Absorption Tests
12.1.3).
2.2 ANSI Standards:
3.3 Definition of Term Specific to This Standard—The
S1.6 Preferred Frequencies, Frequency Levels, and Band
followingtermhasthemeaningnotedforthistestmethodonly:
4
Numbers for Acoustical Measurements
3.3.1 outputinterval, Dt,[T],s—ofareal-timeanalyzer,the
time between successive outputs; this time is not necessarily
the same as the integration time.
1
This test method is under the jurisdiction of ASTM Committee E33 on
EnvironmentalAcousticsandisthedirectresponsibilityofSubcommitteeE33.01on
4. Summary of Test Method
Sound Absorption.
4.1 Measurement of the Sound Absorption of a Room:
Current edition approved Dec. 10, 2002. Published April 2003. Originally
approved in 1958. Last previous edition approved 2002 as C 423 – 02.
4.1.1 A band of random noise is used as a test signal and
2
Annual Book of ASTM Standards, Vol 04.06.
turned on long enough (about the time for 20 dB decay in the
3
Annual Book of ASTM Standards, Vol 14.02.
4 test band with the smallest decay rate) for the sound pressure
Available from American National Standards Institute, 1430 Broadway, New
York, NY 10018. level to reach a steady state. When the signal is turned off, the
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C423–02a
sound pressure level will decrease and the decay rate in each ally
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