ASTM E1704-95

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.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: E 1704 – 95
Standard Guide for
Specifying Acoustical Performance of Sound-Isolating
Enclosures
This standard is issued under the fixed designation E 1704; 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.
1. Scope tional Safety and Health Administration]
2.5 Other Standard:
1.1 The guide covers the development of criteria for the
VDI 2711 Schallschutz durch Kapeslung [Verein Deutscher
acoustical performance of a broad variety of acoustical enclo-
Ingeireure, Beuth Verlag GmbH, Berlin] [German] [Noise
sures by identifying information necessary to unambiguously
Control by the Use of Enclosures]
describe acoustical performance. This guide is not a standard
ASTM specification for a sound-isolating enclosure.
3. Terminology
1.2 Excluded from the scope of this guide are technical
3.1 Definitions:
considerations for enclosure design that do not pertain directly
3.1.1 Standard definitions of acoustical terms may be found
to acoustical performance.
in Terminology C 634.
1.3 This standard does not purport to address all of the
3.2 Definitions of Terms Specific to This Standard:
safety concerns, if any, associated with its use. It is the
3.2.1 A-weighted sound pressure level—sound pressure
responsibility of the user of this standard to establish appro-
level measurements made with the A-weighting filter applied
priate safety and health practices and determine the applica-
as defined in ANSI S1.4, denoted L in this guide.
PA
bility of regulatory limitations prior to use.
3.2.2 C-weighted sound pressure level—sound pressure
2. Referenced Documents level measurements made with the C-weighting filter applied
as defined in ANSI S1.4, denoted L in this guide.
PC
2.1 ASTM Standards:
3.2.3 enclosure—a structure, usually free-standing, which
C 423 Test Method for Sound Absorption and Sound Ab-
substantially or completely encloses a given space or object.
sorption Coefficients by the Reverberation Room Method
This does not include barrier walls, partitions within a building,
C 634 Terminology Relating to Environmental Acoustics
or other partial structures.
E 336 Test Method for Measurement of Airborne Sound
3.2.4 enclosure-generated noise—sound created by the op-
Insulation in Buildings
eration of the enclosure systems, such as lighting and ventila-
E 413 Classification for Rating Sound Insulation
tion.
E 596 Test Method for Laboratory Measurement of the
3.2.5 level reduction—for the purposes of this guide, the
Noise Reduction of Sound-Isolating Enclosures
arithmetic difference between sound pressure levels at a
2.2 ANSI Standards:
specific location before and after the installation of the enclo-
ANSI S1.4 Specification for Sound Level Meters
sure, expressed in decibels.
ANSI S3.1 Maximum Permissible Ambient Noise Levels
3 3.2.6 level reduction specification—specification of the
for Audiometric Test Rooms
acoustical performance of an enclosure by stating the reduction
ANSI S3.6 Specification for Audiometers
in sound pressure level caused by the enclosure.
ANSI S12.31–S12.35 Methods for Determining the Sound
3.2.7 personnel enclosure—an enclosure designed to keep
Power Levels of Machines and Equipment
sound energy from personnel or equipment therein. Examples
2.3 ISO Standard:
of personnel enclosures include but are not limited to audio-
ISO 3741–3745 Acoustics—Methods for Determining the
3 metric booths, in-plant offices, broadcast booths, and acoustical
Sound Power Levels of Machines and Equipment
test chambers.
2.4 Government Standard:
3.2.8 pre-installation sound pressure levels—the sound
29 CFR 1910.95 Occupational Noise Exposure [Occupa-
pressure levels, as a function of frequency, that are present
prior to the installation of the enclosure. In most cases this is
This guide is under the jurisdiction of ASTM Committee E-33 on Environ-
determined by measuring the ambient sound pressure levels in
mental Acoustics and is the direct responsibility of Subcommittee E33.03 on Sound
Transmission.
Current edition approved June 15, 1995. Published August 1995.
2 4
Annual Book of ASTM Standards, Vol 04.06. Available from the Superintendent of Documents, U.S. Government Printing
Available from American National Standards Institute, 11 W. 42nd St., 13th Office, Washington, DC 20402.
Floor, New York, NY 10036. Available from Beuth Verlag GmbH, Burggrafenstrasse 4-7, 1000 Berlin 30.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
E 1704
often estimated from the sound power levels of noise-emitting equipment
the host area but in some cases, such as new construction, the
and a general description of the acoustical properties of the environment.
sound pressure levels must be predicted.
3.2.9 sound pressure level specification—specification of
5.4.2 Determine the maximum permissible sound pressure
the acoustical performance of an enclosure by stating the
levels that must exist at the same locations after the introduc-
maximum sound pressure levels that shall exist after installa-
tion of the enclosure, and
tion.
5.4.3 Determine the required enclosure level reduction. The
3.2.10 source enclosure—an enclosure designed to keep
required isolation is related to the difference between the sound
sound energy from personnel or equipment on the outside.
pressure levels before and after the introduction of the enclo-
Such applications include, but are not limited to, equipment
sure.
silencing, secure communications, music practice, and acous-
5.5 Many specifications are for multiple enclosures or
tical testing.
enclosures with multiple functions, or both. It is beyond the
scope of this guide to provide detailed guidance for every
4. Summary of Guide
possible combination. Separate specifications for each source-
4.1 An explanation of the determination and subsequent
enclosure-receiver combination should be used in such a case.
specification of acoustical performance of sound-isolating
5.6 The type of specification that should be selected de-
enclosures is presented.
pends both on the purpose of the enclosure and how crucial its
4.2 Two types of specifications are described in this guide.
performance is. In general:
The recommended method (sound pressure level specification)
5.6.1 If exceeding a particular maximum permissible sound
is to specify the maximum permissible sound pressure levels
pressure level spectrum would render the enclosure unsuccess-
that may be present after installation of the enclosure. The
ful, a sound pressure level specification should be used.
alternate method (level reduction specification) is to specify the
5.6.1.1 This guide assigns all phases of acoustical design are
enclosure’s level reduction.
delegated to the supplier. Compliance is usually more easily
4.3 The type of specification selected depends largely on the
verified than with the level reduction method.
enclosure application and the data available. A sound pressure
5.6.2 If the criteria for the success of the enclosure are less
level specification usually applies to a specific site, while the
stringent or not related to a specific maximum permissible
level reduction specification may have broader application.
spectrum, a level reduction specification may be used.
Also, the sound pressure level specification is more appropriate
6. Recommended Specifications
where specific sound pressure levels are required, while the
level reduction specification reflects a more general interest in
6.1 The sound pressure level specification specifies the
amounts of noise level reduction.
maximum permissible sound pressure levels that may exist
4.4 Some guidance is provided in Appendix X1 on selecting
either inside or outside the enclosure after installation. Pre-
a specification type based on the enclosure application and the
installation sound pressure levels must also be presented.
information available.
6.1.1 Maximum sound pressure levels should be specified in
4.5 Substantial guidance is given on the essential acoustical
one-third-octave bands whenever possible to allow a detailed
data that must be compiled.
fit to the requirements. Octave band sound pressure levels are
4.6 A non-mandatory model specification Appendix X2 is
appropriate where the noise spectrum is broad band and free of
included that embraces both specification types. It also serves
prominent tones.
as a guide for identifying and gathering information necessary
6.1.2 The desired post-installation sound pressure level may
to the manufacturer for designing the enclosure.
also be described by a single number descriptor, such as
A-weighted sound pressure level or NC or RC ratings. In this
5. Significance and Use
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.
NOTE 2—Other single number ratings for noise may also be available.
5.2 This guide is intended for those familiar with basic
For further information see ASHRAE Handbook.
concepts of acoustics.
5.3 Although this guide provides detailed guidance in mat-
6.1.3 Measured sound pressure levels are preferred. When
ters relating to specification of acoustical enclosures, it is not a
not available, such as in the case of new construction, the
substitute for the experience and judgment of an acoustical or
following information is usually considered an acceptable
noise control professional.
substitute to allow estimation of sound pressure levels:
5.3.1 This guide calls for measurements common within
6.1.3.1 The rated or measured sound power level (here
acoustical practice.
denoted L ) of equipment and,
W
5.3.2 The more critical the performance requirements of the
6.1.3.2 A description of the host environment, including the
enclosure, the more the user should consider seeking the
relative locations of sources of noise, personnel, and the
services of an acoustics or noise control professional.
enclosure. Some loss of accuracy should be expected.
5.4 The specifying of a sound-isolating enclosure has three
6.1.4 Inaccurate measurement of sound pressure levels can
sequential steps:
result from unsteady or intermittent sources of noise during
5.4.1 Determine the sound pressure levels that exist at
specific locations prior to the introduction of the enclosure,
ASHRAE Handbook, Fundamentals, Chapter 7, American Society of Heating,
NOTE 1—In the case of new construction, the sound pressure level is Refrigerating and Air Conditioning Engineers, Atlanta, Georgia.
E 1704
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 be no older than five years.
PC PA
measurements. 6.2.2.4 Laboratory noise reduction data obtained in accor-
dance with Test Method E 596 in prototype testing are often
6.1.5 Maximum permissible sound pressure levels 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 An enclosure may provide the required level reduction
hearing conservation regulations, architectural specifications, without achieving a particular sound pressure level spectrum in
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
7. Other Noise Control Properties of Enclosures
pressure levels should not be exceeded with all sources of
7.1 Vibration Isolation—The effectiveness of an enclosure
enclosure-generated noise in normal operation.
can be compromised by structure-borne noise bypassing the
6.2 The level reduction specification identifies the minimum
acoustical barrier through adjacent building structures. Enclo-
permissible level reduction to be provided by the enclosure.
sures should be isolated from adjacent structures by means of
This type specification is often used by a buyer who has
flexible connections.
already determined the isolation needed to meet his sound
7.1.1 Vibrations that can be felt by the hand are an indica-
pressure level requirements. Using this type of specification
tion that measurements of vibration levels are necessary.
without such analysis could result in unacceptable results.
NOTE 4—In typical installations, structure-borne vibration treatments
6.2.1 Level reduction I(f) can be approximated as follows:
are part of the enclosure. Special cases, for example, broadcast studios,
I f 5 L 2 L 1 SF
~ !
1 2
generally require measurement or analysis of structure-borne vibration
patterns of the host environment prior to specification, or both, where
where:
applicable.
L = pre-installation sound pressure level in a given band,
NOTE 5—The L measurement and treatment of structure-borne vibra-
a
L = post-installation sound pressure level in a given band,
tion are difficult. Measurements are complicated and an ineffective
and
treatment can actually be counterproductive. In critical situations an
SF = safety factor.
expert should be consulted.
6.2.1.1 The safety factor helps ensure compliance by ac-
7.2 Interior Sound Absorption—Most applications benefit
counting for unforeseen complications due to changes in site
from sound absorption within the enclosure. Insufficient sound
conditions, or unusual acoustical interactions of the enclosure
absorption has two effects: a more reverberant sound field can
and the space. The more critical the successful performance of
affect speech intelligibility and the ability to localize sound
the enclosure, the larger the selected safety factor should be.
generated within the enclosure. Low sound absorption can
Typical values are:
reduce sound isolation performance.
Not Critical. SF = 0 dB
7.2.1 Sound absorption is properly expressed in terms of the
Moderate. SF = 3 dB
sound absorption coefficient of the absorbing surfaces deter-
Conservative. SF = 6 dB
mined in a laboratory in accordance with Test Method C 423.
NOTE 3—In practice safety factor siz
...