ASTM E1124-10
(Test Method)Standard Test Method for Field Measurement of Sound Power Level by the Two-Surface Method
Standard Test Method for Field Measurement of Sound Power Level by the Two-Surface Method
SIGNIFICANCE AND USE
The function and operation of equipment in the field often preclude the measurement of the free-field sound pressure levels of a single piece of equipment in the absence of interfering sound from other equipment operating at the same time. The two-surface method will provide, in most cases, a reliable estimate of the normal sound power levels of a specimen operating in an adverse environment.
This test method is intended for use in the field in the presence of what is normally regarded as interfering background noise. This test method is based upon the work of Hubner , and Diehl, but differs from all other current sound power measurement procedures by requiring simultaneous measurement at both conformal surfaces and by resolving time-averaged sound pressure levels at both surfaces to within 0.1 dB. These two features, simultaneous recording and 0.1dB resolution, enable source sound power to be calculated when the direct sound field of the source is actually lower in level than the ambient noise.
The use of this test method is expected to be primarily for the relative assessment of the sound power from similar sources or for the prediction of sound levels in a plant based upon measurements of similar sources in another plant. This test method is believed to be capable of yielding a reasonably good estimate of absolute power level with proper care of application and full conformance to the provisions of this procedure.
The two-surface method is applicable only when the two measurement surfaces can be physically selected to produce positive values of the difference in average sound pressure level. That is, the inner surface sound pressure level minus the outer surface sound pressure level must be at least +0.1 dB. This limitation applies to each frequency band and each constituent surface area investigated. Only the frequency band in which a zero or negative difference occurs is it considered invalid and usually adjacent bands will be valid. In practice, only rar...
SCOPE
1.1 This test method covers the field, or in situ measurement of sound power level by the two-surface method. The test method is designed to minimize the effects of reverberant conditions, directivity of the noise source under consideration, and the effects of ambient noise from other nearby equipment operating at the same time.
1.2 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.
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Designation:E1124 −10
StandardTest Method for
Field Measurement of Sound Power Level by the Two-
1
Surface Method
This standard is issued under the fixed designation E1124; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope method. These are surfaces over which the measuring micro-
phones are swept. They are located at two different distances
1.1 Thistestmethodcoversthefield,or in situmeasurement
from the equipment. Fig. 1 shows a typical arrangement of
of sound power level by the two-surface method. The test
these surfaces for a generalized piece of equipment.
method is designed to minimize the effects of reverberant
3.2.2 constituent surface area—a portion of the conformal
conditions, directivity of the noise source under consideration,
surface.
and the effects of ambient noise from other nearby equipment
operating at the same time.
4. Summary of Test Method
1.2 This standard does not purport to address all of the
4.1 The average one-third or full octave band sound pres-
safety concerns, if any, associated with its use. It is the
sure levels are measured over two different conformal surfaces
responsibility of the user of this standard to establish appro-
which envelop the equipment. These conformal surfaces
priate safety and health practices and determine the applica-
should be selected to consist of rectangular, cylindrical, and
bility of regulatory limitations prior to use.
hemispherical constituent surfaces so that the surface areas
may be easily calculated. From the difference between the two
2. Referenced Documents
2 average sound pressure levels taken at each surface and from
2.1 ASTM Standards:
the areas of the surfaces, the sound power level may be
C634Terminology Relating to Building and Environmental
calculated. The calculation accounts for both the effect of the
Acoustics
reverberant field and the noise of other equipment. It is
3
2.2 ANSI Standard:
permissible to define conformal surfaces that completely en-
S1.4Specification for Sound Level Meters
velope the source, yet only measure over a portion of the
conformalsurfaceduetorestrictionsfromprocessconnections
3. Terminology
or accessibility.
3.1 Definitions—For definitions of terms used in this test
4
method, refer to Terminology C634. 5. Significance and Use
3.2 Definitions of Terms Specific to This Standard: 5.1 The function and operation of equipment in the field
3.2.1 conformal surface—the locus of points which lie at a often preclude the measurement of the free-field sound pres-
fixed distance from the reference surface of a piece of sure levels of a single piece of equipment in the absence of
equipment. Two conformal surfaces are used in this test interfering sound from other equipment operating at the same
time. The two-surface method will provide, in most cases, a
reliable estimate of the normal sound power levels of a
1
ThistestmethodisunderthejurisdictionofASTMCommitteeE33onBuilding
specimen operating in an adverse environment.
and Environmental Acousticsand is the direct responsibility of Subcommittee
E33.08 on Mechanical and Electrical System Noise.
5.2 This test method is intended for use in the field in the
Current edition approved May 1, 2010. Published June 2010. Originally
presence of what is normally regarded as interfering back-
approved in 1986. Last previous edition approved in 1997 as E1124–97. DOI:
ground noise. This test method is based upon the work of
10.1520/E1124-10.
5,6 7
2
Hubner and Diehl, but differs from all other current sound
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
5
the ASTM website. Hubner,G.,“AnalysisofErrorsinMeasuringMachineNoiseUnderFreeField
3
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St., Conditions,” Journal of the Acoustical Society of America,Vol 54, No. 4, 1973, pp.
4th Floor, New York, NY 10036.Available from American National Standards 967–977.
6
Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:// Hubner, G., “Qualification Procedures for Free Field Conditions for Sound
www.ansi.org. Power Determination of Sound Sources and Methods for the Determination of the
4
TerminologyC634–85wastheeditionusedduringthedevelopmentofthistest Appropriate Environmental Correction,” Journal of the Acoustical Society of
method. America, Vol 61, No. 2, 1977, pp. 456–464.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
...
This document is not anASTM standard and is intended only to provide the user of anASTM 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:E1124–97 (Reapproved 2004) Designation: E1124 – 10
Standard Test Method for
Field Measurement of Sound Power Level by the Two-
1
Surface Method
This standard is issued under the fixed designation E1124; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber 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 field, or in situ measurement of sound power level by the two-surface method.The test method
is designed to minimize the effects of reverberant conditions, directivity of the noise source under consideration, and the effects
of ambient noise from other nearby equipment operating at the same time.
1.2 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.
2. Referenced Documents
2
2.1 ASTM Standards:
C634 Terminology Relating to Building and Environmental Acoustics
3
2.2 ANSI Standard:
S1.4 Specification for Sound Level Meters
3. Terminology
4
3.1 Definitions—For definitions of terms used in this test method, refer to Terminology C634.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 conformal surface—the locus of points which lie at a fixed distance from the reference surface of a piece of equipment.
Two conformal surfaces are used in this test method. These are surfaces over which the measuring microphones are swept. They
are located at two different distances from the equipment. Fig. 1 shows a typical arrangement of these surfaces for a generalized
piece of equipment.
3.2.2 constituent surface area—a portion of the conformal surface.
4. Summary of Test Method
4.1 The average one-third or full octave band sound pressure levels are measured over two different conformal surfaces which
envelop the equipment. These conformal surfaces should be selected to consist of rectangular, cylindrical, and hemispherical
constituentsurfacessothatthesurfaceareasmaybeeasilycalculated.Fromthedifferencebetweenthetwoaveragesoundpressure
levels taken at each surface and from the areas of the surfaces, the sound power level may be calculated.The calculation accounts
for both the effect of the reverberant field and the noise of other equipment. It is permissible to define conformal surfaces that
completely envelope the source, yet only measure over a portion of the conformal surface due to restrictions from process
connections or accessibility.
5. Significance and Use
5.1 The function and operation of equipment in the field often preclude the measurement of the free-field sound pressure levels
of a single piece of equipment in the absence of interfering sound from other equipment operating at the same time. The
1
This test method is under the jurisdiction ofASTM Committee E33 on Building and EnvironmentalAcoustics and is the direct responsibility of Subcommittee E33.08
on Mechanical and Electrical System Noise.
Current edition approvedAprilMay 1, 2004.2010. PublishedApril 2004.June 2010. Originally approved in 1986. Last previous edition approved in 1997 as E1124–97.
DOI: 10.1520/E1124-97R04.10.1520/E1124-10.
2
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@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.
3
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036.Available from American National Standards Institute
(ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
4
Terminology C634 – 85 was the edition used during the development of 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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E1124 – 10
FIG. 1 Configuration of Conformal Surfaces, General Case
two-surface method will provide, in most cases, a reliable estimate of the normal sound power levels of a specimen operating in
an adverse environment.
5.2 Thistestmethodisintendedforuseinthefieldinthepresenceofwhatisnormallyregardedasin
...
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