1、Designation: E 477 06aStandard Test Method forMeasuring Acoustical and Airflow Performance of DuctLiner Materials and Prefabricated Silencers1This standard is issued under the fixed designation E 477; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the laboratory testing of someof the acoustical properties of s
3、ound attenuating devicesincluding duct liner materials, integral ducts, and in-ductabsorptive straight and elbow silencers used in the ventilationsystems of buildings. Procedures are described for the mea-surement of acoustical insertion loss, airflow generated noise,and pressure drop as a function
4、of airflow.1.2 Excluded from the scope are reactive mufflers and thosedesigned for uses other than in ventilation systems, such asautomobile mufflers.1.3 This test method includes a provision for a simulatedsemi-reflective plenum to fit around thin-walled duct andsilencer test specimens, since the a
5、coustical environmentsaround such thin-walled specimens can affect the measuredinsertion loss.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health pra
6、ctices and determine the applica-bility of regulatory limitations prior to use.1.5 This method tests the performance of the specimen inwell-defined and controlled conditions. If the specimen isinstalled in the field in any different manner, the results may bedifferent. This standard does not provide
7、 estimating proceduresfor determining the actual installed performance of the speci-men field conditions.2. Referenced Documents2.1 ASTM Standards:2C 384 Test Method for Impedance and Absorption ofAcoustical Materials by Impedance Tube MethodC 423 Test Method for Sound Absorption and Sound Ab-sorpti
8、on Coefficients by the Reverberation Room MethodC 634 Terminology Relating to Environmental AcousticsE90 Test Method for Laboratory Measurement of AirborneSound Transmission Loss of Building Partitions and Ele-mentsE 795 Practices for Mounting Test Specimens DuringSound Absorption Tests2.2 ANSI Stan
9、dards:3S1.11994(R2004) Acoustical TerminologyS1.112004 Specification Octave, Half-Octave and Third-Octave Band Filter SetsS12.512002/ISO 3741:1999 Acoustics-Determination ofSound Power Levels of Noise Sources Using SoundPressure-Precision Method for Reverberation Rooms2.3 AMCA Standards:4AMCA 300 96
10、, Reverberant Room Method for SoundTesting of Fans2.4 ASHRAE Documents and Standards:52001ASHRAE Handbook, Fundamentals Volume, Chapter14, Chapter on Measurement and InstrumentsANSI/ASHRAE 41.3 Method for Pressure Measurement2.5 NAIMA Documents and Standards:6Fibrous Glass Duct Liner Standard 3rd ed
11、., 20023. Terminology3.1 DefinitionsThe acoustical terms used in this methodare consistent with Terminology C 634, and ANSI S1.1.3.2 Definitions of Terms Specific to This Standard:3.2.1 acoustical duct liner materiala material that hassound absorptive properties and is attached to the inside wall of
12、a duct to attenuate the sound that propagates down that sectionof duct.3.2.2 airflow generated noisethe noise created by aerody-namic turbulence caused by air flowing through a device.3.2.3 background noisethe total of all noise sources ofinterference in a system used for the production, detection,1
13、This test method is under the jurisdiction of ASTM Committee E33 onEnvironmentalAcoustics and is the direct responsibility of Subcommittee E33.08 onMechanical and Electrical System Noise.Current edition approved May 1, 2006. Published May 2006. Originallyapproved in 1973. Last previous edition appro
14、ved in 2006 as E 477 06.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Sta
15、ndards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.4Available from Air Movement and Control Association, 30 W. University Dr.,Arlington Heights, IL 60004.5Available from American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. (ASHRAE), 1791 Tullie Circle,
16、NE, Atlanta, GA30329.6Available from North American Insulation Manufactures Association(NAIMA) 44 Canal Center Plaza, Suite 310 Alexandria, VA 22314.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.measurement, or recording of a signa
17、l, independent of thepresence of the signal.3.2.4 empty duct measurementsacoustical measurementsof sound propagation through the duct system when no testspecimen is inserted in this system.3.2.5 equivalent diameter of rectangular ducts4(W 3 H)/P1/2, where W and H are the width and height ofthe duct
18、specimen connection, respectively.3.2.6 forward flow ( + )(a) The condition where air flowsthrough a sound attenuating device in the same direction as thepropagation of sound; (b) the air flow from the noise sourcechamber to the reverberation room (through the duct system).3.2.7 in-duct sound-attenu
19、ating devicesunits designed toreduce the sound that transmits through a duct system.3.2.8 insertion loss (IL)the reduction in sound powerlevel, in decibels, due solely to the placement of a sound-attenuating device in the path of transmission, for example, thetest duct system, between a sound source
20、 and the givenlocation-which in this standard is the reverberation room.3.2.9 integral ducta duct formed from an integral com-posite of materials, typically having a porous inner layer toprovide sound absorption, with an impervious outer surface.3.2.10 noise source chamber an enclosure, near one end
21、of the duct system, in which one or more sources are locatedfor the purpose of generating sound, which is transmittedthrough the duct system to the reverberation room, located atthe other end.3.2.11 reverse flow ()(a) The condition where air flowsthrough a sound attenuating device in the opposite di
22、rection tothe propagation of sound; (b) the airflow from the reverberationroom to the noise source chamber (through the duct system).3.2.12 standard air density (ds)1.202 kg/m3(0.075 lb/ft3).This corresponds approximately to dry air at 21C (70F) and101.3 kPa (29.92 in. Hg).3.2.13 static pressure at
23、a plane of traverse, Ps, Pa (in.water)the arithmetic average of the static pressure at pointsin the plane of traverse.3.2.14 static pressure at a point, P8s, Pa (in. water)thepressure measured by the static connection of a pitot tubepointed upstream at that point.3.2.15 test runpertains to all readi
24、ngs and calculations atany one setting of the air flow throttling device.3.2.16 thin-walled ducta duct or silencer whose wall massor stiffness are low enough to allow significant energy toescape into the surrounding environment. This term applies toducts whose walls are thinner than 24 gage, or are
25、flexible, orare of rigid fiberglass construction.3.2.17 total pressure at a plane of traverse, Pt, Pa (in.water)the algebraic sum of the velocity pressure at the planeof traverse and the static pressure at the plane of traverse.3.2.18 traversea series of readings made with a pitot tubein a cross sec
26、tion of the test duct, perpendicular to the ductlength, in accordance with 2001 ASHRAE Handbook, Chapter14 Measurement and Instruments.3.2.19 velocity pressure at a plane of traverse, Pv, Pa (in.water)the square of the average of the square roots of thevelocity pressures at points in the plane of tr
27、averse.3.2.20 velocity pressure at a point, P8v, Pa (in. water)thepressure measured by the differential reading of a pitot tubepointed upstream at that point.3.3 Symbols:see ASHRAE Fundamentals Handbook 20013.3.1 D = air density in reverberation room, kg/m3(lb/ft3).3.3.2 BP = barometric pressure, kP
28、a (in. Hg).3.3.3 td= dry bulb temperature, C (F).3.3.4 T = absolute temperature of air in reverberation room,K (C + 273) or R = (F + 460).3.3.5 Pv= velocity pressure at a plane of transverse, Pa (in.water).3.3.6 Ps= static pressure at a plane of transverse, Pa (in.water).3.3.7 V = average velocity i
29、n the duct across the plane oftraverse, m/s (ft/min).3.3.8 DP = pressure differential or pressure drop across thein-duct sound attenuating device, Pa (in. water).3.3.9 Q = discharge rate, L/s (ft3/min).3.3.10 K = values of constant K.3.3.11 A2= orifice area, m2(ft2).Gc= gravitational conversion fact
30、or, 9.806 m/s2(32.174 ft/s2).3.3.12 hf = pressure drop obtained by the pressure taps, Pa(lbf/ft2).4. Summary of Test Method4.1 To measure the insertion loss of a test specimen, twoseparate measurements must be made. The sound pressurelevel in the reverberation room is measured while sound isentering
31、 the room through a length of straight or elbow emptyduct with a sound source at the far end. The sound pressurelevel in the reverberation room is measured again after asection of the empty duct has been replaced with the testspecimen. The insertion loss is equal to the difference betweenthe two mea
32、sured sound pressure levels.4.2 The airflow generated noise is measured in terms offrequency band sound power levels while only air flow and noadditional fan noise or noise from the noise source chamberpasses through the specimen under test.4.3 Pressure drop performance is obtained by measuring thes
33、tatic pressure at designated locations upstream and down-stream of the test specimen at various airflow settings. Thepressure drop and airflow may be measured with a variety ofstandard acceptable instrumentation such as piezometer rings,flow nozzles, orifices, etc. However, the method describedherei
34、n is the pitot tube and manometer method.5. Significance and Use5.1 Specimens tested using this standard, for example, ductsilencers, are used to control sound propagation throughventilation ducts. The results gathered from testing specimensto this standard can be used to estimate the reduction in f
35、ansound levels in ducted airflow systems caused by including asound attenuating device in the system. The device can be acomponent in a source-path-receiver analysis where calcula-tions are performed to determine the resultant sound level in anoccupied space. Proper selection of a sound attenuating
36、devicecan enable a designer to achieve in-space background noisecriteria.E 477 06a25.2 The insertion loss of a silencer is a matter of degree, andvaries with frequency and with the direction and speed ofairflow. Because silencers partially obstruct the air path andprovide resistance to airflow, two
37、other effects must be quan-tified: pressure drop and airflow-generated noise. Both increasewith increasing air speeds; thus data are required for severalairflows to correctly characterize performance.5.3 The aerodynamic results from testing specimens to thestandard can be used as information for the
38、 system designengineer to determine the amount of static pressure dropresistance to be overcome by the system fan(s). Guidelines forappropriate maximum allowable pressure drop for a soundattenuating element have been established in the design com-munity and are based on the procedures described here
39、in.5.4 As stated previously in 1.5 of this test method, the actualperformance of a sound attenuating device as installed in an airduct system may be significantly different than reported basedon the test procedure herein. This standard does not provideguidance to the user on these system effects.5.5
40、 Silencers are often designed to be used under conditionswhich do not duplicate the test set-ups of this standard.Mock-ups and specialized test set-ups to determine perfor-mance of sound attenuating devices in non-standard configu-rations may be based on this test method but cannot beconsidered to b
41、e in full conformance with this test method. SeeAnnex A2 for further information regarding such tests.6. Test Facilities6.1 The test facility shall consist of a signal source chamberand a reverberation room coupled together by means of alength of straight or elbow duct. Provisions shall be made inth
42、e duct system for inserting either a test specimen, or a sectionof empty duct having the same interior cross-sectional dimen-sions at the duct connection points, length, and shape (forelbow testing) as the test specimen. An example of a facilityset-up to accommodate straight silencer testing is show
43、n in Fig.1. An example of a facility setup to accommodate elbowsilencer testing (at various angles) is shown in Fig. 2. Airflowand noise source plenum(s) may be at a fixed or a mobilelocation within the test facility to accommodate straight and/orelbow silencer testing.6.2 Signal Source ChamberThe s
44、ignal source chambershall be an enclosure large enough to accommodate one ormore sound sources. The sound source system shall be struc-turally isolated from the chamber and duct system. Thisenclosure should be joined to the duct system through anopening in the chamber having dimensions the same as o
45、rgreater than the duct. In the latter case, a tapered transitionpiece is placed between the duct and the opening in thechamber.6.2.1 The signal source chamber should be constructed ofmaterial having sufficient sound transmission loss and beadequately isolated to reduce the possibility of sound enter
46、ingthe reverberation room by paths other than through the ductconnecting the signal source chamber and reverberation room.6.2.2 In order to ensure that the reaction on the sound sourceremains essentially constant with or without the test specimenin place, the interior wall surfaces of the signal sou
47、rce chambermust be lined with sound-absorbing material. The materialshall have a minimum NRC = 0.25, as determined by TestMethod C 423 and TypeAmounting per Practices E 795 for allthe test frequencies but should be kept low enough so that thesound pressure level in the reverberation room is 10 dB ab
48、oveambient when the test specimen is in place and the soundsource is on.6.2.3 The physical size of the signal source chamber shall besuch that no inside dimension is less than the largest dimensionof the duct system and that the sound source is totally enclosedand does not obstruct the opening into
49、the duct.FIG. 1 Typical Facility for Rating Straight Duct Silencers With or Without AirflowE 477 06a36.2.4 A second duct may be attached to the signal sourcechamber through which quiet airflow can be supplied to thesystem.6.3 Duct System (Between Source Chamber and Reverbera-tion Room)The construction of the duct system shall be ofadequate mass (14 gage or heavier steel) so that any environ-mental or flanking noises entering the duct system have anegligible effect on the measurements. When testing highinsertion loss silencers, it may be nece
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