ASTM C423-01

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-Jul-2001
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• 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 C423-00 - Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method
• Effective Date: 10-Jul-2001
• Replaced By: ASTM C423-02 - Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method
• Effective Date: 10-Apr-2002
• Referred By: ASTM C1482-23 - Standard Specification for Polyimide Flexible Cellular Thermal and Sound Absorbing Insulation
• Effective Date: 10-Jul-2001
• Referred By: ASTM E795-23 - Standard Practices for Mounting Test Specimens During Sound Absorption Tests
• Effective Date: 10-Jul-2001
• Referred By: ASTM D4851-07(2019)e1 - Standard Test Methods for Coated and Laminated Fabrics for Architectural Use
• Effective Date: 10-Jul-2001
• Referred By: ASTM E3091-17 - Standard Specification for Systems to Measure Sound Levels
• Effective Date: 10-Jul-2001
• Referred By: ASTM D5456-21e1 - Standard Specification for Evaluation of Structural Composite Lumber Products
• Effective Date: 10-Jul-2001
• Referred By: ASTM E1042-22 - Standard Classification for Acoustically Absorptive Materials Applied by Trowel or Spray
• Effective Date: 10-Jul-2001
• Referred By: ASTM E1111/E1111M-14(2022) - Standard Test Method for Measuring the Interzone Attenuation of Open Office Components
• Effective Date: 10-Jul-2001
• Referred By: ASTM E596-22 - Standard Test Method for Laboratory Measurement of Noise Reduction of Sound-Isolating Enclosures
• Effective Date: 10-Jul-2001
• Referred By: ASTM E2235-04(2020) - Standard Test Method for Determination of Decay Rates for Use in Sound Insulation Test Methods
• Effective Date: 10-Jul-2001
• Referred By: ASTM E492-22 - Standard Test Method for Laboratory Measurement of Impact Sound Transmission Through Floor-Ceiling Assemblies Using the Tapping Machine
• Effective Date: 10-Jul-2001
• Referred By: ASTM E2963-22 - Standard Test Method for Laboratory Measurement of Acoustical Effectiveness of Ship Noise Treatments Laboratory Measurement of Acoustical Effectiveness for Marine Bulkhead and Deck Treatments
• Effective Date: 10-Jul-2001
• Referred By: ASTM C634-22 - Standard Terminology Relating to Building and Environmental Acoustics
• Effective Date: 10-Jul-2001
• Referred By: ASTM E1374-18e1 - Standard Guide for Office Acoustics and Applicable ASTM Standards
• Effective Date: 10-Jul-2001

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: C 423 – 01
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
nex A2), and reverberation room qualification (see Annex A3).
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
following term has the meaning noted for this test method only:
4
Numbers for Acoustical Measurements
3.3.1 output interval, Dt, [T], s—of a real-time analyzer, 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
4. Summary of Test Method
Environmental Acoustics and is the direct responsibility of Subcommittee E-33.01
on Sound Absorption.
4.1 Measurement of the Sound Absorption of a Room:
Current edition approved July 10, 2001. Published September 2001. Originally
4.1.1 A band of random noise is used as a test signal and
published as C 423-58-T. Last previous edition C 423 – 00.
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.
test band with the smallest decay rate) for the sound pressure
4
Available from American National Standards Institute, 1430 Broadway, New
level to reach a steady state. When the signal is turned off, the
York, NY 10018.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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C 423
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sound pressure level will decrease
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