1、STDOBSI BS EN IS0 11820-ENGL 1777 1b24bb9 Ob40132 507 Acoustics - Measurements on silencers in situ * cn * The European Standard EN IS0 11820 : 1996 has the status of a British Standard ICs 17.140.01 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN IS0 11820 : 1997 BS EN
2、IS0 11820 : 1997 Amd. No. This British Standard, having been prepared under the direction of the Health and Environment Sector Board, was published under the authority of the Standards Board and comes into effect on 15 September 1997 O BSI 1997 Date Text affected National foreword This British Stand
3、ard is the English language version of EN IS0 11820 : 1996. It is identical with IS0 11820 : 1996. The UK participation in its preparation was entrusted by Technical Commitke EW1, Acoustics, to Subcommittee EW1/4, Machinery noise, which has the responsibility to: - aid enquirers to understand the te
4、xt; - present to the responsible hternationai/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed - monitor related international and European developments and promulgate them in the UK A list of organizations represented on this subcom
5、mittee can be obtained on request to its secretary. Cross-references Attention is dram to the fact that CEN and CENELEC Standards nody include an annex which lists normative references to international publications with their corresponding European publications. The British Standards which implement
6、 these international or European publications may be found in the BSI Standards Catalogue under the section entitled International Standards Correspondence Index, or using the Find facility of the BSI Standards Electronic Caalogue. Compliance with a British Standard does not of itself confer immunit
7、y from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, the EN IS0 title page, EN IS0 foreword page, the IS0 title page, pages ii to iv, pages 1 to 18, the annex ZA page, a blank page, an inside back cover and a back cover. ISBN O 680 28444 i STD*BSI
8、BS EN IS0 11820-ENGL 1977 1b24bb7 Ob40134 381 W EUROPEAN STANDARD NORME EUROPENNE E U RO P i SCH E NORM EN IS0 11820 December 1996 ICs 17.140.40; 91.140.30 Descriptors: See IS0 document English version Acoustics - Measurements on silencers in situ (IS0 1 1820: 1996) Acoustique - Mesurages sur silenc
9、ieux in situ (IS0 11820:1996) * ui * This European Standard was approved by CEN on 1996-11-07. CEN members are bound to comply with the CENKENELEC Internai Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-dat
10、e lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. The European Standards exist in three official versions (English, French, German). A version in any other made by translation under the responsibi
11、lity of a CEN member into its own language and notified to the Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Swe
12、den, Switzerland and United Kingdom. CEN European Comnittee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart,% 6-1050 Brussels anguage Centra 1 celand, 0 1996 Copyright reserved to CEN members Ref. No. EN IS0 11820:1996 E STDOBSI
13、BS EN IS0 11820-ENGL 1777 M Lb2irbbS Ob40135 218 9 EN IS0 11820 : 1996 Foreword The text of the International Standard IS0 1 1820:1996 has been prepared by Technical Committee ISO/TC 43 “Acoustics“ in collaboration with Technical Committee CEN/TC 21 1 “Acoustics“, the secretariat of which is held by
14、 DS. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 1997, and conflicting national standards shall be withdrawn at the latest by June 1997. According to the CENICENELEC Internal Regulations,
15、 the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Endorsem
16、ent notice The text of the International Standard IS0 11820:1996 was approved by CEN as a European Standard without any modification. NOTE: Normative references to International Standards are listed in annex ZA (normative). EN IS0 11820 : 1996 INTERNATIONAL STANDARD IS0 11 820 First edition 1996-12-
17、15 Acoustics - Measurements on silencers in situ Acoustique - Mesurages sur silencieux in situ Reference number IS0 11820:1996() STD-BSI BS EN IS0 118ZIO-ENGL I997 Ib211bb9 Ob40137 090 EN IS0 11820 : 1996 Contents 1 2 3 4 5 6 7 8 9 Scope Normative references Definitions Corrections for background no
18、ise 4.1 4.2 Insertion sound pressure level difference . Installation conditions Measuring instruments 6.1 Acoustic instruments 6.2 Air flow. static pressure and temperature measuring devices . Test object and measuring conditions . Transmission sound pressure level difference . Measurement procedu r
19、es 8.1 General . 8.2 Acoustic measurements . 8.3 Flow. pressure and temperature measurements Evaluation 9.1 Evaluation of sound pressure measurements 9.2 Evaluation of flow measurements . 10 Information to be recorded 11 Information to be reported . Annexes A Field corrections B Calibration of direc
20、tional microphones and microphones equipped with a turbulence windscreen C Bibliography . Page 1 2 2 4 4 5 5 5 5 7 7 7 7 7 9 10 10 12 13 14 15 17 18 Descriptors: acoustics. noise (sound). engine noise. noise reduction. silencers. tests. field tests. performance tests. acoustic tests. acceptance test
21、ing. acoustic measurements . i STD-BSI BS EN IS0 11820-ENGL 1997 Lb2LibbS b40138 T27 EN IS0 11820 : 1996 Foreword IS0 (the International Organization for Standardization) is a worldwide fed- eration of national standards bodies (IS0 member bodies). The work of preparing Intemational Standards is nor
22、mally carried out through IS0 technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non- governmental, in liaison with ISO, also take part in
23、 the work. IS0 collab- orates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are cir- culated to the member bodies for voting. Publication as an International Stand
24、ard requires approval by at least 75 % of the member bodies casting a vote. International Standard IS0 1 1820 was prepared by Technical Committee ISOTTC 43, Acoustics, Subcommittee SC 1, Noise. Annexes A to C of this International Standard are for information only. iii Introduction This Intemational
25、 Standard gives a method for evaluating the acoustic performance of silencers under plant-operating conditions. The attenuation losses determined express the extent to which the level of sound power passing through a duct, or across the internal cross-section of an aperture or opening (e.g. in an en
26、closure or a building) is reduced by the use of a silencer. Sound transmission via flanking elements is attributed to the silencer performance unless the flanking element is not a patt of the silencer or of the related duct walls. The influences of flow noise and of alterations to the operating cond
27、itions with and without a silencer are included. In laboratory measurements on ducted silencers in accordance with IS0 7235, insertion losses, static pressure losses and regenerated sound (flow noise) are determined under well-defined conditions. In practical ap- plications both the sound field and
28、flow field are less uniformly distributed. This can lead to different attenuations and greater pressure losses. In ad- dition, sound levels and rates of flow are mutually dependent. Therefore, in this International Standard the regenerated sound is not measured separ- ately but is treated as a prope
29、rty of the silencer in its operating installation which limits the degree of attenuation in the particular application. iv STD-BSI BS EN IS0 11820-ENGL 1997 Lb24bb9 Ob4014O b5 W EN IS0 11820 : 1996 Acoustics - Measurements on silencers in sfu 1 Scope 1 .I This International Standard specifies measur
30、e- ments on silencers in situ. It is applicable to measure- ments on silencers in practical applications for acoustic analysis, acceptance tests and similar evaluations. Results obtained in accordance with this International Standard cannot be compared to per- formance data obtained from laboratory
31、measure- ments on ducted silencers in accordance with IS0 7235, partly because of different test conditions (such as sound field distribution, flow, temperature and mounting conditions) and partly because of different definitions. Depending on the method used, the measurement is either of - insertio
32、n loss Di, or - transmission loss Dts. The measurement method depends upon the type of silencer and the installation conditions (e.g. insertion loss measurements must be carried out for blowdown silencers). NOTE 1 The subscripts denote the practical application of the silencer and the particular ins
33、tallation and operating conditions: “s“ stands for “in situ“, “t“ for transmission. and “i“ for insertion. Additional characteristic quantities, which could in- clude measurements taken using artificial sound sources or measurements taken to determine the di- rectivity of sound propagation from the
34、silencer, may be agreed upon in accordance with this International Standard. 1.2 This International Standard is applicable to a) silencers which are installed either as a whole or in the form of individual baffles in the propagation path of sound (e.g. openings of ducts) originating from a sound sou
35、rce (machine, building, plant such as a gas turbine generator, scrubbing plant, cooling tower, heating ventilation and air con- ditioning (HVAC) plant, exhaust stack, air intake duct, weapon, intemal combustion engine, com- pressor, etc.); all types of passive silencers (absorptive, reac- tive, refl
36、ection and blowdown silencer); active silencers (involving amplifiers and loud- speakers) as far as the insertion loss of passive silencers is equivalent to the off/on conditions of active devices; and other measures or means of effecting acoustic attenuation in air or other gases (e.9. components i
37、nstalled in ducting, louvres, grilles and deflector hoods). Additionally, this International Standard is applicable to !he determination of the effect of cleaning or refurbish- ing silencers, This International Standard is not applicable to closed high-pressure systems (e.g. silencers in closed pipe
38、s) since measurements of structure-borne sound are not anticipated. 1.3 Quantities to be measured include the following: a) sound pressure levels in octave bands with centre frequencies at least from 63 Hz to 4 kHz and, if possible and required, from 31,5 Hz to 8 kHz or in one-third-octave bands wit
39、h centre frequencies from 50 Hz to 5 kHz and, if possible and required, from 25 Hz to 10 kHz - at a point or points on the source side of a silencer, - at a point or points on the receiver side of a silencer; b) static and dynamic pressures, flow velocities and temperatures at selected positions. Op
40、erating data to be determined include flow rate, pressure and speed, which define the operating con- ditions of the machine or plant to be silenced. 1 EN IS0 11820 : 1996 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of
41、 this Intemational Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this Intemational Standard are encouraged to in- vestigate the possibility of applying the most recent editions of the standards indic
42、ated below. Members of IEC and IS0 maintain registers of currently valid Inter- national Standards. IS0 3744:1994, Acoustics - Determination of sound power levels of noise sources using sound press- ure - Engineering method in an essentially free field over a reflecting plane. IS0 5221 :1984, Air di
43、stribution and air diffusion - Rules to methods of measuring air flow fate in an air handling duct. IEC 651 :1979, Sound level meters. IEC 651 :1979/Amd.l:1993, Amendment No. 7. IEC 804: 1 985, lntegraiing-averaging sound level meters. IEC 804:1985/Amd.l:1989, Amendment No. 1. IEC 804:1985/Amd.2:199
44、3, Amendment No. 2. 3 Definitions For the purposes of this International Standard, the following definitions apply. 3.1 transmission sound pressure level differ- ence, Dtps: Difference, in decibels, between the mean sound pressure levels on the source and receiver side of a silencer: - Dtps = Lp2 -
45、LpI . . . (1) where - Lpl is the mean sound pressure level (ref. 20pPa), in decibels (in one-third-octave or octave bands, see IEC 1260), on the receiver side of the silencer, for all measuring points used to determine the airborne sound within the duct or propagated from the aperture and external s
46、urfaces of the silencer; - Lp2 is the mean sound pressure level (ref. 20pPa), in decibels (in one-third-octave or octave bands), on the source side of the silencer, for all measuring points used to de- termine the airborne sound reaching the silencer. NOTE 2 DM is not self-standing but is an interme
47、di- ate step towards determining the transmission loss (see 9.1.3). Mean sound pressure levels are defined by . . . (2) where LPj is the individual level; N is the number of measuring points. 3.2 insertion sound pressure level difference, Dips: Difference, in decibels, in sound pressure levels measu
48、red at a point or averaged over a small meas- urement area before and after installation of a silencer: qps = Lpll - LpI . . . (3) where 41 LpiI is the sound pressure level (ref. 20pPa), in decibels (in one-third-octave or octave bands, see IEC 1260), of the sound source(s) measured at a point or av
49、eraged over a small measurement area, after installation of the silencer; is the sound pressure level (ref. 20pPa), in decibels (in one-third-octave or octave bands), occurring at the same measuring point or over a small measurement area due to the sound source(s) to which the silencer is to be attached, before installation of the silencer. NOTE3 As opposed to %s, qps is restricted to a point or a small area where certain directivity indices of sound radiation with and without the silencer are effec- tive. The reference to a small area with a diameter of about ha
