1、Designation: E477 13Standard Test Method forLaboratory Measurements of Acoustical and AirflowPerformance of Duct Liner Materials and PrefabricatedSilencers1This standard is issued under the fixed designation E477; the number immediately following the designation indicates the year oforiginal adoptio
2、n or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the laboratory testing of someof the acoustical pro
3、perties of sound 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
4、 a function 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,
5、 since the acoustical environmentsaround such thin-walled specimens can affect the measuredinsertion loss.1.4 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. Thi
6、s standard does not provide estimating proceduresfor determining the actual installed performance of the speci-men under field conditions.1.5 The values stated in SI units are to be regarded asstandard. The values in parentheses are provided for informa-tion only.1.6 This standard does not purport t
7、o 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 practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C634 Ter
8、minology Relating to Building and EnvironmentalAcoustics2.2 ANSI Standards:3S1.11994(R2004) Acoustical TerminologyS1.112004(R2009) Specification Octave, Half-Octave andThird-Octave Band Filter SetsS1.43-1997(R2007) Specifications for Integrating-Averaging Sound Level MetersS12.5-2006/ISO 6926:1999(R
9、2011) Requirements for thePerformance and Calibration of Reference Sound SourcesUsed for the Determination of Sound Power LevelsS12.512012/ISO 3741:2010 Acoustics-Determination ofSound Power Levels of Noise Sources Using SoundPressure-Precision Method for Reverberation Rooms2.3 ASHRAE Documents and
10、Standards:42009 ASHRAE Handbook, Fundamentals,Chapter 36, Mea-surement and InstrumentsANSI/ASHRAE 41.3-1989 Standard Method for PressureMeasurement (plus errata dated 5 January 1998)2.4 NAIMA Documents and Standards:5Fibrous Glass Duct Liner Standard, Publication AH124,Third Edition, 20023. Terminol
11、ogy3.1 DefinitionsThe acoustical terms used in this methodare consistent with Terminology C634, and ANSI S1.1.3.2 Definitions of Terms Specific to This Standard:1This test method is under the jurisdiction ofASTM Committee E33 on Buildingand Environmental Acoustics and is the direct responsibility of
12、 SubcommitteeE33.08 on Mechanical and Electrical System Noise.Current edition approved June 1, 2013. Published August 2013. Originallyapproved in 1973. Last previous edition approved in 2006 as E477 06a. DOI:10.1520/E0477-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcon
13、tact 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 Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4Availabl
14、e from American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. (ASHRAE), 1791 Tullie Circle, NE, Atlanta, GA30329, http:/www.ashrae.org.5Available from North American Insulation Manufacturers Association(NAIMA), 44 Canal Center Plaza, Suite 310, Alexandria, VA 22314, http:/w
15、ww.naima.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.1 acoustical duct liner materiala material that hassound absorptive properties and is attached to the inside wall ofa duct to attenuate the sound that propagates down th
16、at sectionof duct.3.2.2 airflow generated noisethe sound created by aero-dynamic turbulence caused by air flowing through a device.3.2.3 background noisethe total sound pressure level ofall noise sources of interference in a system used for theproduction, detection, measurement, or recording of a si
17、gnal,independent of the presence of the signal.3.2.4 dynamic insertion lossinsertion loss measured withair flowing through the test specimen.3.2.5 empty duct measurementsacoustical measurementsof sound propagation through the duct system when no testspecimen is inserted in this system.3.2.6 end refl
18、ection loss (ERL)sound energy reflectedback into the duct at the termination of duct into a large space.3.2.7 equivalent diameter of rectangular ducts4(WH)/1/2, where W and H are the width and height ofthe duct specimen connection, respectively.3.2.8 forward flow ( + )(a) the condition where air flo
19、wsthrough a sound attenuating device in the same direction as thepropagation of sound; (b) the airflow from the sound sourcechamber to the reverberation room (through the duct system).3.2.9 in-duct sound-attenuating devicesa device or systemintended to reduce the sound power propagating inside the d
20、uctfrom one duct section to another.3.2.10 insertion loss (IL)the reduction in sound powerlevel, in decibels, due to the placement of a sound-attenuatingdevice in the path of transmission, for example, the test ductsystem, between a sound source and the given location-whichin this standard is the re
21、verberation room.3.2.11 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.3.2.12 reference sound source (RSS)a portable, aerody-namic sound source that produces a known stable broadb
22、andsound power output.3.2.13 reverse flow ()(a) the condition where air flowsthrough a sound attenuating device in the opposite direction tothe propagation of sound; (b) the airflow from the reverberationroom to the sound source chamber (through the duct system).3.2.14 sound source chamber an enclos
23、ure, near one endof 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.3.2.15 standard air density (ds)1.202 kg/m3. This corre-sponds approximately to dry air at
24、21C and 101.3 kPa.3.2.16 static pressure at a plane of traverse, (Ps),Pathearithmetic average of the static pressure at points in the planeof traverse.3.2.17 static pressure at a point, (Ps), Pathe pressuremeasured by the static connection of a pitot tube pointedupstream at that point.3.2.18 test ru
25、npertains to all measurements and calcula-tions at any one setting of the airflow throttling device.3.2.19 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 th
26、inner than 0.6 mm, or are flexible, orare of rigid glass fiber construction.3.2.20 total pressure at a plane of traverse, (Pt), Pathealgebraic sum of the velocity pressure at the plane of traverseand the static pressure at the plane of traverse.3.2.21 traversea series of measurements made with a pit
27、ottube in a cross section of the test duct, perpendicular to the ductlength, in accordance with the ASHRAE Fundamentals Hand-book Chapter on Measurement and Instruments.3.2.22 velocity pressure at a plane of traverse, (Pv), Pathesquare of the average of the square roots of the velocitypressures at p
28、oints in the plane of traverse.3.2.23 velocity pressure at a point, (Pv), Pathe pressuremeasured by the differential measurement of a pitot tubepointed upstream at that point.4. Summary of Test Method4.1 Insertion loss is measured by comparing the change insound pressure level due to the insertion o
29、f a test specimen intoa duct system connecting a reverberation room to a soundsource chamber. When insertion loss is measured with airflowing through the test specimen, the measured quantity isdynamic insertion loss. The sound signal is created by a systemof loudspeakers within the sound source cham
30、ber and trans-mitted through the system ductwork to the reverberation room.The intent of the method is that the airborne path through theduct is the dominant means of sound transmission between thesound source chamber and the reverberation room. Measure-ments are made in a series of frequency bands
31、becauseinsertion loss is a function of frequency.4.2 Noise generated by air flowing through the test speci-men is measured in the reverberation room and expressed interms of a computed sound power level within each frequencyband.4.3 Pressure drop performance is obtained by measuring thestatic pressu
32、re 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 describedherein is the pit
33、ot tube and manometer method.4.4 It is the intent of this test method that corrections due tobackground and flanking noise be eliminated or minimized asmuch as possible. Where corrections are unavoidable, the dataare to be marked as corrected and shall indicate the magnitudeof the corrections made a
34、s described in Sections 9 and 10.5. 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 specimensE477 132to 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. Correct selection of a sound attenuating
36、 devicecan enable a designer to achieve in-space background noisecriteria.5.2 The insertion loss of a silencer varies with frequencyand with the direction and speed of airflow. Because silencerspartially obstruct the air path and provide resistance to airflow,two other effects must be quantified: pr
37、essure drop andairflow-generated noise. Both increase with increasing airspeeds; thus data are required for several airflows to correctlycharacterize performance.5.3 The aerodynamic results from testing specimens to thestandard can be used as information for the system designengineer to determine th
38、e 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 herein.5.4 As stated previously in 1.4 of
39、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 Silencers are often designed to be us
40、ed 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 be in full conformance with this test m
41、ethod. SeeAnnex A2 for further information regarding such tests.6. Test Facilities6.1 The test facility shall consist of a sound source chamberand a reverberation room coupled together by means of alength of straight or elbow duct. Provisions shall be made inthe duct system for inserting either a te
42、st 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 shown in Fig.1. An example of a facility se
43、t-up to accommodate elbowsilencer testing (at various angles) is shown in Fig. 2. Airflowand sound source chamber may be at a fixed or a mobilelocation within the test facility to accommodate straight and/orelbow silencer testing.6.2 Signal Source ChamberThe sound source chambershall be a device (as
44、 shown schematically in Fig. 1) containingtwo openings if testing will be conducted with airflow throughthe test specimen. One opening connects to the test duct andthe reverberation chamber, and the other opening connects tothe duct from the fan system. The sound source chamberopenings for these two
45、 ducts shall have the same dimensions(or larger) as the connecting duct. It is recommended that aflared (tapered) opening be provided for the test duct tominimize flow generated noise. The recommended soundsource chamber opening dimension is 2 times the duct dimen-sion for the test duct connecting t
46、o the reverberation chamber.The sound source (loudspeaker) shall be structurally isolatedfrom the sound source chamber and the connecting ductsystems. The sound source chamber shall be large enough toaccommodate one or more sound sources with a minimumclearance between the sound source diaphragm and
47、 the soundsource chamber walls of at least 250 mm in all directions. Therecommended minimum volume of the sound source chamberis 10 m3.FIG. 1 Typical Facility for Rating Straight Duct Silencers With or Without AirflowE477 1336.2.1 The sound source chamber shall be constructed ofmaterials having suff
48、icient sound transmission loss and beadequately isolated from the surrounding environment tominimize noise from the sound source from entering thereverberation chamber by any path other than the duct contain-ing the test specimen. It may be necessary to install soundabsorbing materials on the inside
49、 surface of the sound sourcechamber walls to meet the sound source chamber qualification(see 6.2.2).6.2.2 The sound source chamber shall be tested to ensurethat the acoustic energy transmitted into the test duct is notaffected by the insertion of the test sample by passing thefollowing qualification test.6.2.2.1 The positioning of the loudspeaker(s) shall be thesame during routine testing and sound source chamber quali-fication.6.2.2.2 A measurement microphone (meeting the require-ments of section 6.6) shall be used to monitor and qualify the
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