ASTM E477-99
(Test Method)Standard Test Method for Measuring Acoustical and Airflow Performance of Duct Liner Materials and Prefabricated Silencers
Standard Test Method for Measuring Acoustical and Airflow Performance of Duct Liner Materials and Prefabricated Silencers
SCOPE
1.1 This test method covers the laboratory testing of duct liner materials, integral ducts, and in-duct absorptive silencers used in the ventilation systems of buildings. Procedures are described for the measurement of acoustical insertion loss, airflow generated noise, and pressure drop as a function of airflow.
1.2 Excluded from the scope are reactive mufflers and those designed for uses other than in ventilation systems, such as automobile mufflers.
1.3 This test method includes a provision for a simulated semi-reflective plenum to fit around thin-walled duct and silencer test specimens, since the acoustical environments around such thin-walled specimens can affect the measured insertion loss.
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.
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Designation: E 477 – 99
Standard Test Method for
Measuring Acoustical and Airflow Performance of Duct
Liner Materials and Prefabricated Silencers
This standard is issued under the fixed designation E477; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 ANSI Standards:
S1.1 Acoustical Terminology
1.1 This test method covers the laboratory testing of duct
S1.11 Octave, Half-Octave and Third-Octave Band Filter
liner materials, integral ducts, and in-duct absorptive straight
Sets
and elbow silencers used in the ventilation systems of build-
S1.13 Measurement of Sound Pressure Levels
ings. Procedures are described for the measurement of acous-
S12.31-1990, Precision Methods for the Determination of
tical insertion loss, airflow generated noise, and pressure drop
Sound Power Levels of Broad-Band Noise Sources in
as a function of airflow.
Reverberation Rooms
1.2 Excluded from the scope are reactive mufflers and those
2.3 ASME Test Codes:
designed for uses other than in ventilation systems, such as
ANSI/ASME PTC 11-1984 (R1990) Fans
automobile mufflers.
ASME MFC-3M (1989)
1.3 This test method includes a provision for a simulated
ASME 19.5-72
semi-reflective plenum to fit around thin-walled duct and
2.4 AMCA Standards:
silencer test specimens, since the acoustical environments
ANSI/AMCA 210-85
around such thin-walled specimens can affect the measured
AMCA 300
insertion loss.
2.5 ASHRAE Documents and Standards:
1.4 This standard does not purport to address all of the
ASHRAE Handbook, Fundamentals Volume (current edi-
safety concerns, if any, associated with its use. It is the
tion), Chapter on Measurement and Instruments
responsibility of the user of this standard to establish appro-
ANSI/ASHRAE 41.2-1987 (RA92) Standard Methods for
priate safety and health practices and determine the applica-
Laboratory Airflow Measurement
bility of regulatory limitations prior to use.
2.6 ISO Standards:
2. Referenced Documents
ISO 3741
ISO 7235
2.1 ASTM Standards:
C423 Test Method for Sound Absorption and Sound Ab-
3. Terminology
sorption Coefficients by the Reverberation Room Method
2 3.1 Definitions—The acoustical terms used in this method
C634 Terminology Relating to Environmental Acoustics
are consistent with Terminology C634,ANSI S1.1, andANSI
E90 Test Method for Laboratory Measurement ofAirborne
2 S1.13.
Sound Transmission Loss of Building Partitions
3.2 Definitions of Terms Specific to This Standard:
E548 Guide for General Criteria Used for Evaluating
3 3.2.1 acoustical duct liner material—a material that has
Laboratory Competence
soundabsorptivepropertiesandisattachedtotheinsidewallof
E717 Guide for Preparation of the Accreditation Annex of
a duct to attenuate the sound that propagates down that section
Acoustical Test Standards
of duct.
E 795 Practices for Mounting Test Specimens During
Sound Absorption Tests
Available from American National Standards Institute, 11 W. 42nd St., 13th
This test method is under the jurisdiction of ASTM Committee E-33 on Floor, New York, NY 10036.
EnvironmentalAcousticsandisthedirectresponsibilityofSubcommitteeE33.08on Available fromAmerican Society of Mechanical Engineers, 345 East 47th St.,
Mechanical and Electrical System Noise. New York, NY 10017.
Current edition approved October 10, 1999. Published January 2000. Originally Available from Air Movement and Control Association, 30 W. University Dr.,
published as E477–73. Last previous edition E477–96. Arlington Heights, IL 60004.
2 7
Annual Book of ASTM Standards, Vol 04.06. Available from ASHRAE, 1791 Tullie Circle, NE, Atlanta, GA 30329.
3 8
Annual Book of ASTM Standards, Vol 14.02. Available from ISO, Case Postale 56, CH-1211, Genève 20, Switzerland.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 477
3.2.2 airflow generated noise—the noise generated by air 3.2.19 velocity pressure at a plane of traverse, P , Pa (in.
v
flowing through a device. water)—the square of the average of the square roots of the
velocity pressures at that point.
3.2.3 background noise—the total of all noise sources of
interference in a system used for the production, detection, 3.2.20 velocity pressure at a point, P8 , Pa (in. water)—the
v
measurement, or recording of a signal, independent of the pressure measured by the differential reading of a pitot tube
presence of the signal. pointed upstream at that point.
3.2.4 empty duct measurements—the sound pressure levels 3.3 Symbols:Symbols—see ASHRAE Fundamentals Hand-
measured in the reverberation room as a result of the noise
book, Measurement and Instruments chapter:
3 3
generated by the sound sources in the source chamber and
3.3.1 D =air density in reverberation room, kg/m (lb/ft ).
transmitted through the empty duct system without the test
3.3.2 BP =barometric pressure, kPa (in. Hg).
specimen inserted.
3.3.3 t =dry bulb temperature, °C(°F).
d
3.2.5 equivalent diameter of rectangular ducts—
3.3.4 T =absolutetemperatureofairinreverberationroom,
1/2
{4(W 3H)/P} , where W and H are the width and height of
K(°C+273) or [°R=(°F+460)].
the duct, respectively.
3.3.5 P =velocity pressure at a plane of transverse, Pa (in.
v
3.2.6 forward flow (+)—noise that propagates in the same
water).
direction as airflow.
3.3.6 P =static pressure at a plane of transverse, Pa (in.
s
3.2.7 in-duct sound-attenuating devices—units specifically
water).
designed to be installed in a ventilating duct system for the
3.3.7 V =average velocity in the duct across the plane of
purpose of attenuating the sound that transmits through the
traverse, m/min (ft/min).
in-duct sound-attenuating device.
3.3.8 DP =pressure differential or pressure drop across the
3.2.8 insertion loss (IL)—the reduction in sound power
in-duct sound attenuating device, Pa (in. water).
level, in decibels, at a given location due solely to the
3.3.9 Q =discharge rate, L/s (ft /s).
placement of a sound-attenuating device in the path of trans-
mission between the sound source and the given location. The 3.3.10 K =values of constant K.
2 2
path of transmission in this case is within the test duct system.
3.3.11 A =orifice area, m (ft ).
3.2.9 integral duct—a duct formed from an integral com-
G =gravitational conversion factor, 9.806 m/s (32.174 ft/
c
posite of materials, typically having a porous inner layer to
s ).
provide sound absorption, with an impervious outer surface.
3.3.12 hf =pressure drop obtained by the pressure taps, Pa
3.2.10 reverse flow (−)—noise that propagates in the oppo-
(lbf/ft ).
site direction to airflow.
3.2.11 signalsourcechamber—anenclosureattheupstream
4. Summary of Test Method
endoftheductsysteminwhichoneormoresoundsourcesare
4.1 To measure the insertion loss of a test specimen, two
located for the purpose of generating sound to be transmitted
separate measurements must be made. The sound pressure
through the duct system and discharged into the receiving
level in the reverberation room is measured while sound is
reverberation room.
entering the room through a length of straight or elbow empty
3 3
3.2.12 standard air density (d )—1.202 kg/m (0.075 lb/ft ).
s
duct with a sound source at the far end. The sound pressure
This corresponds approximately to dry air at 21°C (70°F) and
level in the reverberation room is measured again after a
101.3 kPa (29.92 in. Hg).
section of the empty duct has been replaced with the test
3.2.13 static pressure at a plane of traverse, P , Pa (in.
s
specimen.The insertion loss is equal to the difference between
water)—the arithmetic average of the static pressure at points
thetwomeasuredsoundpressurelevels.Thesectionofstraight
in the plane of traverse.
empty duct is designed to have negligible attenuation at all
3.2.14 static pressure at a point, P8 , Pa (in. water)—the
s measurement frequencies. The construction of the test facility
pressure measured by the static connection of a pitot tube
duct system and the shape of the test elbow silencer determine
pointed upstream at that point.
thegeometryoftheelbowemptyduct.Theelbowductmustbe
3.2.15 test run—pertains to all readings and calculations at
fully described in all test reports to include information on the
any one setting of the throttling device. shape, angle, radius, centerline, and so on, due to different
elbow constructions having various attenuation properties.
3.2.16 thin-walledduct—aductorsilencerwhosewallmass
or stiffness are low enough to allow significant energy to
4.2 The airflow generated noise is measured in terms of
escape into the environment about it (low STC). This term
frequency band sound power levels while air, originally quiet,
applies to ducts whose walls are thinner than 24 gage, or are
is passing through the system with the test specimen installed.
flexible, or are of rigid fiberglass construction.
4.3 Pressuredropperformanceisobtainedbymeasuringthe
3.2.17 total pressure at a plane of traverse, P, Pa (in.
static pressure at designated locations upstream and down-
t
water)—the algebraic sum of the velocity pressure at the plane
stream of the test specimen at various airflow settings. The
of traverse and the static pressure at the plane of traverse.
pressure drop and airflow may be measured with a variety of
3.2.18 traverse—a series of readings made with a pitot tube standard acceptable instrumentation such as piezometer rings,
inside a duct in accordance with ASHRAE Fundamentals flow nozzles, orifices, etc. However, the method described
Handbook, Measurement and Instruments chapter. herein is the pitot tube and manometer method.
E 477
5. Significance and Use turally isolated from the chamber and duct system. This
enclosure should be joined to the duct system through an
5.1 The procedures described are for measurement of the
opening in the chamber having dimensions the same as or
properties of silencing elements as installed in a laboratory
greater than the duct. In the latter case, a tapered transition
facility of the type described herein.The insertion loss, airflow
piece is placed between the duct and the opening in the
generated noise, and pressure drop of a silencer in an actual
chamber.
installation may differ from the values obtained from this test
6.2.1 The signal source chamber should be constructed of
methodduetointeractionwithotherelementsoftheventilation
material having sufficient sound transmission loss and be
system. Provisions have been included for surrounding a
adequately isolated to reduce the possibility of sound entering
thin-walled test specimen with a simulated semi-reflective
the reverberation room by paths other than through the duct
plenum.
connecting the signal source chamber and reverberation room.
5.2 Silencersareoftendesignedtobeusedunderconditions
6.2.2 Inordertoensurethatthereactiononthesoundsource
which do not duplicate the duct-to-duct test set-up covered in
remains essentially constant with or without the test specimen
this test standard. Mock-up or specialized test set-ups for such
inplace,theinteriorwallsurfacesofthesignalsourcechamber
silencers (such as those to be used at the end of a duct) are not
must be lined with sound-absorbing material. The material
considered to be in full conformance with this standard. See
shall have a minimum NRC=0.25, as determined by Test
Annex A2 for information regarding such tests.
MethodC423andTypeAmountingperPracticesE795forall
the test frequencies but should be kept low enough so that the
6. Test Facilities
sound pressure level in the reverberation room is 10 dB above
6.1 The test facility shall consist of a signal source chamber
ambient when the test specimen is in place and the sound
and a reverberation room coupled together by means of a
source is on.
length of straight or elbow duct. Provisions shall be made in
6.2.3 Thephysicalsizeofthesignalsourcechambershallbe
theductsystemforinsertingeitheratestspecimen,orasection
suchthatnoinsidedimensionislessthanthelargestdimension
of empty duct having the same interior cross-sectional dimen-
oftheductsystemandthatthesoundsourceistotallyenclosed
sions at the duct connection points, length, and shape (for
and does not obstruct the opening into the duct.
elbow testing) as the test specimen. An example of a facility
6.2.4 A second duct may be attached to the signal source
set-up to accomodate straight silencer testing is shown in Fig.
chamber through which quiet airflow can be supplied to the
1. An example of a facility set–up to accommodate elbow
system.
silencer testing (at various angles) is shown in Fig. 2. Airflow
and noise source plenum(s) may be at a fixed or a mobile 6.3 Duct System (Between Source Chamber and Reverbera-
location within the test facility to accommodate straight and/or tion Room)—The construction of the duct system shall be of
elbow silencer testing. adequate mass (14 gage or heavier steel) so that any environ-
6.2 Signal Source Chamber—The signal source chamber mental or flanking noises entering the duct system have a
shall be an enclosure large enough to accommodate one or negligible effect on the measurements. When testing high
more sound sources. The sound source system shall be struc- insertionlosssilencers,itmaybenecessarytoapplyadamping
FIG. 1 Typical Facility for Rating Straight Duct Silencers With or Without Airflow
E 477
FIG. 2 Typical Facility for Rating Elbow Duct Silencers With or Without Airflow
material to the outside of the duct walls or increase the than 7.5°). The duct shall terminate at the reverberation room
wall abruptly with the same cross-sectional dimensions as the
transmission loss, or both, by adding one or more layers of
gypsum board to the exterior. The interior surface of the duct system duct.
system shall be smooth and have a low sound absorption
6.3.3 There are occasions when a silence, designed to be
coefficient in the frequency range of interest.
used at the termination of a duct system, must be tested.
Testing of such silencers, mounted at the termination of the
6.3.1 The length of the duct system is primarily determined
facility duct or in the reverberation room, shall be considered
by the requirements of air-flow measurements.The duct length
a special circumstance, and shall be noted as an exception to
upstream, regardless of the shape of the test specimen and
this test standard in the test report. Full details concerning the
layout of test facility, shall be not less than 5 equivalent
mounting and testing must al
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