ASTM E1704-95(2002)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:E1704–95 (Reapproved 2002)
Standard Guide for
Specifying Acoustical Performance of Sound-Isolating
Enclosures
This standard is issued under the fixed designation E1704; 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 ANSI S12.31–S12.35 Methods for Determining the Sound
Power Levels of Machines and Equipment
1.1 The guide covers the development of criteria for the
2.3 ISO Standard:
acoustical performance of a broad variety of acoustical enclo-
ISO 3741–3745 Acoustics—Methods for Determining the
sures by identifying information necessary to unambiguously
Sound Power Levels of Machines and Equipment
describe acoustical performance. This guide is not a standard
2.4 Government Standard:
ASTM specification for a sound-isolating enclosure.
29 CFR 1910.95 Occupational Noise Exposure [Occupa-
1.2 Excluded from the scope of this guide are technical
tional Safety and Health Administration]
considerations for enclosure design that do not pertain directly
2.5 Other Standard:
to acoustical performance.
VDI 2711 Schallschutz durch Kapeslung [Verein Deutscher
1.3 This standard does not purport to address all of the
Ingeireure, Beuth Verlag GmbH, Berlin] [German] [Noise
safety concerns, if any, associated with its use. It is the
Control by the Use of Enclosures]
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
3. Terminology
bility of regulatory limitations prior to use.
3.1 Definitions:
2. Referenced Documents 3.1.1 Standard definitions of acoustical terms may be found
in Terminology C634.
2.1 ASTM Standards:
3.2 Definitions of Terms Specific to This Standard:
C423 Test Method for Sound Absorption and Sound Ab-
3.2.1 A-weighted sound pressure level—sound pressure
sorption Coefficients by the Reverberation Room Method
level measurements made with the A-weighting filter applied
C634 Terminology Relating to Building and Environmental
as defined in ANSI S1.4, denoted L in this guide.
PA
Acoustics
3.2.2 C-weighted sound pressure level—sound pressure
E336 Test Method for Measurement of Airborne Sound
level measurements made with the C-weighting filter applied
Attenuation between Rooms in Buildings
as defined in ANSI S1.4, denoted L in this guide.
E413 Classification for Rating Sound Insulation PC
3.2.3 enclosure—a structure, usually free-standing, which
E596 Test Method for Laboratory Measurement of Noise
substantially or completely encloses a given space or object.
Reduction of Sound-Isolating Enclosures
Thisdoesnotincludebarrierwalls,partitionswithinabuilding,
2.2 ANSI Standards:
3 or other partial structures.
ANSI S1.4 Specification for Sound Level Meters
3.2.4 enclosure-generated noise—sound created by the op-
ANSI S3.1 Maximum Permissible Ambient Noise Levels
3 eration of the enclosure systems, such as lighting and ventila-
for Audiometric Test Rooms
tion.
ANSI S3.6 Specification for Audiometers
3.2.5 level reduction—for the purposes of this guide, the
arithmetic difference between sound pressure levels at a
ThisguideisunderthejurisdictionofASTMCommitteeE33onEnvironmental specific location before and after the installation of the enclo-
Acoustics and is the direct responsibility of Subcommittee E33.03 on Sound
sure, expressed in decibels.
Transmission.
3.2.6 level reduction specification—specification of the
Current edition approved June 15, 1995. PublishedAugust 1995. DOI: 10.1520/
acousticalperformanceofanenclosurebystatingthereduction
E1704-95R02.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
in sound pressure level caused by the enclosure.
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. Available from the Superintendent of Documents, U.S. Government Printing
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St., Office, Washington, DC 20402.
4th Floor, New York, NY 10036, http://www.ansi.org. Available from Beuth Verlag GmbH, Burggrafenstrasse 4-7, 1000 Berlin 30.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1704–95 (2002)
3.2.7 personnel enclosure—an enclosure designed to keep 5.3.1 This guide calls for measurements common within
sound energy from personnel or equipment therein. Examples acoustical practice.
of personnel enclosures include but are not limited to audio- 5.3.2 The more critical the performance requirements of the
metricbooths,in-plantoffices,broadcastbooths,andacoustical enclosure, the more the user should consider seeking the
test chambers. services of an acoustics or noise control professional.
3.2.8 pre-installation sound pressure levels—the sound 5.4 The specifying of a sound-isolating enclosure has three
pressure levels, as a function of frequency, that are present sequential steps:
prior to the installation of the enclosure. In most cases this is 5.4.1 Determine the sound pressure levels that exist at
determined by measuring the ambient sound pressure levels in specific locations prior to the introduction of the enclosure,
the host area but in some cases, such as new construction, the
NOTE 1—In the case of new construction, the sound pressure level is
sound pressure levels must be predicted.
often estimated from the sound power levels of noise-emitting equipment
3.2.9 sound pressure level specification—specification of
and a general description of the acoustical properties of the environment.
the acoustical performance of an enclosure by stating the
5.4.2 Determine the maximum permissible sound pressure
maximum sound pressure levels that shall exist after installa-
levels that must exist at the same locations after the introduc-
tion.
tion of the enclosure, and
3.2.10 source enclosure—an enclosure designed to keep
5.4.3 Determine the required enclosure level reduction. The
sound energy from personnel or equipment on the outside.
requiredisolationisrelatedtothedifferencebetweenthesound
Such applications include, but are not limited to, equipment
pressure levels before and after the introduction of the enclo-
silencing, secure communications, music practice, and acous-
sure.
tical testing.
5.5 Many specifications are for multiple enclosures or
enclosures with multiple functions, or both. It is beyond the
4. Summary of Guide
scope of this guide to provide detailed guidance for every
4.1 An explanation of the determination and subsequent
possible combination. Separate specifications for each source-
specification of acoustical performance of sound-isolating
enclosure-receiver combination should be used in such a case.
enclosures is presented.
5.6 The type of specification that should be selected de-
4.2 Two types of specifications are described in this guide.
pends both on the purpose of the enclosure and how crucial its
The recommended method (sound pressure level specification)
performance is. In general:
is to specify the maximum permissible sound pressure levels
5.6.1 If exceeding a particular maximum permissible sound
that may be present after installation of the enclosure. The
pressure level spectrum would render the enclosure unsuccess-
alternatemethod(levelreductionspecification)istospecifythe
ful, a sound pressure level specification should be used.
enclosure’s level reduction.
5.6.1.1 Thisguideassignsallphasesofacousticaldesignare
4.3 Thetypeofspecificationselecteddependslargelyonthe
delegated to the supplier. Compliance is usually more easily
enclosure application and the data available. A sound pressure
verified than with the level reduction method.
level specification usually applies to a specific site, while the 5.6.2 If the criteria for the success of the enclosure are less
level reduction specification may have broader application.
stringent or not related to a specific maximum permissible
Also,thesoundpressurelevelspecificationismoreappropriate spectrum, a level reduction specification may be used.
where specific sound pressure levels are required, while the
6. Recommended Specifications
level reduction specification reflects a more general interest in
amounts of noise level reduction.
6.1 The sound pressure level specification specifies the
4.4 Some guidance is provided inAppendix X1 on selecting
maximum permissible sound pressure levels that may exist
a specification type based on the enclosure application and the
either inside or outside the enclosure after installation. Pre-
information available.
installation sound pressure levels must also be presented.
4.5 Substantial guidance is given on the essential acoustical
6.1.1 Maximumsoundpressurelevelsshouldbespecifiedin
data that must be compiled.
one-third-octave bands whenever possible to allow a detailed
4.6 A non-mandatory model specification Appendix X2 is
fit to the requirements. Octave band sound pressure levels are
included that embraces both specification types. It also serves
appropriate where the noise spectrum is broad band and free of
as a guide for identifying and gathering information necessary
prominent tones.
to the manufacturer for designing the enclosure.
6.1.2 The desired post-installation sound pressure level may
also be described by a single number descriptor, such as
5. Significance and Use
A-weighted sound pressure level or NC or RC ratings. In this
event the pre-installation one-third-octave band sound pressure
5.1 This guide can be used to produce a specification for the
levels at or around the installation site shall also be provided.
acoustical performance of an enclosure.
5.2 This guide is intended for those familiar with basic
NOTE 2—Other single number ratings for noise may also be available.
concepts of acoustics.
For further information see ASHRAE Handbook.
5.3 Although this guide provides detailed guidance in mat-
ters relating to specification of acoustical enclosures, it is not a
substitute for the experience and judgment of an acoustical or
ASHRAE Handbook, Fundamentals, Chapter 7, American Society of Heating,
noise control professional. Refrigerating and Air Conditioning Engineers, Atlanta, Georgia.
E1704–95 (2002)
6.1.3 Measured sound pressure levels are preferred. When detailed information on noise source and its pre-installation
not available, such as in the case of new construction, the surroundings should accompany the specification. In addition,
following information is usually considered an acceptable a larger safety factor should be considered.
substitute to allow estimation of sound pressure levels:
6.2.2 The level reduction of enclosures is typically quanti-
6.1.3.1 The rated or measured sound power level (here
fied by the manufacturer in laboratory prototype testing. Noise
denoted L ) of equipment and,
reduction (NR) is measured per Test Method E596, and noise
W
6.1.3.2 Adescription of the host environment, including the
isolation class (NIC) is calculated per Classification E413. For
relative locations of sources of noise, personnel, and the
the purposes of this guide, noise reduction data are an
enclosure. Some loss of accuracy should be expected.
acceptable equivalent for level reduction.
6.1.4 Inaccurate measurement of sound pressure levels can
6.2.2.1 Custom designs are typically not tested, due to cost.
result from unsteady or intermittent sources of noise during
6.2.2.2 The actual enclosure being specified may differ in
measurement, changes in site conditions after measurement
certain particulars from prototypes tested.
(for example, significant sources of noise arising between
6.2.2.3 Because of variations in manufacturing materials
measurement and installation), strong low frequency content
and methods and changes in test standards, test results should
(L −L > 15), and general inexperience with acoustical
PC PA
be no older than five years.
measurements.
6.2.2.4 Laboratory noise reduction data obtained in accor-
6.1.5 Maximum permissible sound pressure levels are often
dance with Test Method E596 in prototype testing are often
prescribed for particular applications by standards or regula-
accepted as performance verification.
tory documents. A short list includes, but is not limited to,
6.2.3 Anenclosuremayprovidetherequiredlevelreduction
hearing conservation regulations, architectural specifications,
withoutachievingaparticularsoundpressurelevelspectrumin
human comfort, speech intelligibility, speech privacy, and
the protected space. As an example, sound pressure levels
acoustical test standards. Common specific cases are cited in
inside an enclosure will be considerably higher when the
Appendix X1.
enclosure is located in a high ambient noise area.
6.1.6 The maximum permissible interior or exterior sound
pressure levels should not be exceeded with all sources of
7. Other Noise Control Properties of Enclosures
enclosure-generated noise in normal operation.
6.2 Thelevelreductionspecificationidentifiestheminimum 7.1 Vibration Isolation—The effectiveness of an enclosure
permissible level reduction to be provided by the enclosure.
can be compromised by structure-borne noise bypassing the
This type specification is often used by a buyer who has acoustical barrier through adjacent building structures. Enclo-
already determined the isolation needed to meet his sound
sures should be isolated from adjacent structures by means of
pressure level requirements. Using this type of specification
flexible connections.
without such analysis could result in unacceptable results.
7.1.1 Vibrations that can be felt by the hand are an indica-
6.2.1 Level reduction I(f) can be approximated as follows:
tion that measurements of vibration levels are necessary.
I f! 5L 2L 1SF
~
1 2
NOTE 4—In typical installations, structure-borne vibration treatments
are part of the enclosure. Special cases, for example, broadcast studios,
where:
generally require measurement or analysis of structure-borne vibration
L = pre-installation sound pressure level in a given band,
patterns of the host environment prior to specification, or both, where
L = post-installation sound pressure level in a given band,
applicable.
and
NOTE 5—The L measurement and treatment of structure-borne vibra-
a
SF = safety factor.
tion are difficult. Measurements are complicated and an ineffective
6.2.1.1 The safety factor helps ensure compliance by ac-
treatment can actually be counterproductive. In critical situations an
counting for unforeseen complications due to changes in site
expert should be consulted.
condit
...