1、BRITISH STANDARD BS EN ISO 11820:1997 Acoustics Measurements on silencers in situ The European Standard EN ISO 11820:1996 has the status of a British Standard ICS 17.140.01BSENISO11820:1997 This British Standard, having been prepared under the directionof the Health and Environment Sector Board, was
2、 published under the authority of the Standards Board and comes into effect on 15 September1997 BSI 09-1999 ISBN 0 580 28444 1 National foreword This British Standard is the English language version of EN ISO11820:1996. It is identical with ISO11820:1996. The UK participation in its preparation was
3、entrusted by Technical Committee EH/1, Acoustics, to Subcommittee EH/1/4, Machinery noise, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK
4、interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this subcommittee can be obtained on request to its secretary. Cross-references Attention is drawn to the fact that CEN and CENELEC Standards normally inc
5、lude an annex which lists normative references to international publications with their corresponding European publications. The British Standards which implement these international or European publications may be found in the BSI Standards Catalogue under the section entitled “International Standa
6、rds Correspondence Index”, or using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard d
7、oes not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, theEN ISO title page, page 2, the ISO title page, pagesii toiv, pages1 to16 and a back cover. This standard has been updated (see copyright date) and
8、 may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBSENISO11820:1997 BSI 09-1999 i Contents Page National foreword Inside front cover Foreword 2 Foreword iii Text of ISO 11820 1ii b
9、lankEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO11820 December1996 ICS17.140.40; 91.140.30 Descriptors: See ISO document English version Acoustics Measurements on silencers in situ (ISO 11820:1996) Acoustique Mesurages sur silencieux in situ (ISO 11820:1996) This European Standard was ap
10、proved by CEN on1996-11-07. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national st
11、andards 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 language made by translation under the responsibility of a CEN member into its own language and notified t
12、o the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN
13、 European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1996 Copyright reserved to CEN members Ref. No. EN ISO 11820:1996 EENISO11820:1996 BSI 09-1999 2 Foreword The text of the International Stand
14、ard ISO11820:1996 has been prepared by Technical Committee ISO/TC43 “Acoustics” in collaboration with Technical Committee CEN/TC211 “Acoustics”, the secretariat of which is held by DS. This European Standard shall be given the status of a national standard, either by publication of an identical text
15、 or by endorsement, at the latest by June1997, and conflicting national standards shall be withdrawn at the latest by June1997. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, B
16、elgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the UnitedKingdom. Endorsement notice The text of the International Standard ISO11820:1996 was approved by CEN as a European Standard without any modi
17、fication. NOTENormative references to International Standards are listed inAnnex ZA (normative).ENISO11820:1996 ii BSI 09-1999 Contents Page Foreword iii Introduction 1 1 Scope 1 2 Normative references 2 3 Definitions 2 4 Corrections for background noise 4 4.1 Transmission sound pressure level diffe
18、rence 4 4.2 Insertion sound pressure level difference 5 5 Installation conditions 5 6 Measuring instruments 5 6.1 Acoustic instruments 5 6.2 Air flow, static pressure and temperature measuring devices 7 7 Test object and measuring conditions 7 8 Measurement procedures 7 8.1 General 7 8.2 Acoustic me
19、asurements 7 8.3 Flow, pressure and temperature measurements 9 9 Evaluation 10 9.1 Evaluation of sound pressure measurements 10 9.2 Evaluation of flow measurements 12 10 Information to be recorded 12 11 Information to be reported 13 Annex A (informative) Field corrections 14 Annex B (informative) Ca
20、libration of directional microphones and microphones equipped with a turbulence windscreen 15 Annex C (informative) Bibliography 15 Annex ZA (normative) Normative references to international publications withtheir relevant European publications 16 Figure 1 General scheme for transmission and inserti
21、on loss measurementsofsilencers 6 Figure 2 Examples of measurement surfaces 8 Table 1 Corrections for background noise 5 Descriptors: Acoustics, noise (sound), engine noise, noise reduction, silencers, tests, field tests, performance tests, acoustic tests, acceptance testing, acoustic measurements.E
22、NISO11820:1996 BSI 09-1999 iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body intere
23、sted 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 the work. ISO collaborates closely with the International Electrotechnical
24、Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least75% of the member bodies casting a vote. Intern
25、ational Standard ISO11820 was prepared by Technical Committee ISO/TC43, Acoustics, Subcommittee SC 1, Noise. Annex A toAnnex C of this International Standard are for information only.iv blankENISO11820:1996 BSI 09-1999 1 Introduction This International Standard gives a method for evaluating the acou
26、stic 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 enclosure or a building) is reduced by the use of
27、a silencer. Sound transmission via flanking elements is attributed to the silencer performance unless the flanking element is not a part of the silencer or of the related duct walls. The influences of flow noise and of alterations to the operating conditions with and without a silencer are included.
28、 In laboratory measurements on ducted silencers in accordance with ISO7235, insertion losses, static pressure losses and regenerated sound (flow noise) are determined under well-defined conditions. In practical applications both the sound field and flow field are less uniformly distributed. This can
29、 lead to different attenuations and greater pressure losses. In addition, sound levels and rates of flow are mutually dependent. Therefore, in this International Standard the regenerated sound is not measured separately but is treated as a property of the silencer in its operating installation which
30、 limits the degree of attenuation in the particular application. 1 Scope 1.1 This International Standard specifies measurements on silencers in situ. It is applicable to measurements on silencers in practical applications for acoustic analysis, acceptance tests and similar evaluations. Results obtai
31、ned in accordance with this International Standard cannot be compared to performance data obtained from laboratory measurements on ducted silencers in accordance with ISO7235, partly because of different test conditions (such as sound field distribution, flow, temperature and mounting conditions) an
32、d partly because of different definitions. Depending on the method used, the measurement is either of insertion loss D is , or transmission loss D ts . The measurement method depends upon the typeofsilencer and the installation conditions (e.g.insertion loss measurements must be carried out for blow
33、down silencers). NOTE 1The subscripts denote the practical application of thesilencer and the particular installation and operating conditions: “s” stands for “in situ”, “t” for transmission, and “i” for insertion. Additional characteristic quantities, which could include measurements taken using ar
34、tificial sound sources or measurements taken to determine the directivity of sound propagation from the 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 i
35、ndividual baffles in the propagation path of sound (e.g. openings of ducts) originating from a sound source (machine, building, plant such as a gas turbine generator, scrubbing plant, cooling tower, heating ventilation and air conditioning (HVAC) plant, exhaust stack, air intake duct, weapon, intern
36、al combustion engine, compressor, etc.); b) all types of passive silencers (absorptive, reactive, reflection and blowdown silencer); c) active silencers (involving amplifiers and loudspeakers) as far as the insertion loss of passive silencers is equivalent to the off/on conditions of active devices;
37、 and d) other measures or means of effecting acoustic attenuation in air or other gases (e.g. components installed in ducting, louvres, grilles and deflector hoods). Additionally, this International Standard is applicable to the determination of the effect of cleaning or refurbishing silencers. This
38、 International Standard is not applicable to closed high-pressure systems (e.g. silencers in closed pipes) 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 f
39、rom63Hz to4kHz and, if possible and required, from31,5Hz to8kHz or in one-third-octave bands with centre frequencies from50Hz to5kHz and, if possible and required, from25Hz to10kHz 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) stat
40、ic and dynamic pressures, flow velocities and temperatures at selected positions. Operating data to be determined include flow rate, pressure and speed, which define the operating conditions of the machine or plant to be silenced.ENISO11820:1996 2 BSI 09-1999 2 Normative references The following sta
41、ndards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged t
42、o investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 3744:1994, Acoustics Determination of sound power levels of noise sources using sound pressure Engineering me
43、thod in an essentially free field over a reflecting plane. ISO 5221:1984, Air distribution and air diffusion Rules to methods of measuring air flow rate in an air handling duct. IEC 651:1979, Sound level meters. IEC 651:1979/Amd.1:1993, Amendment No. 1. IEC 804:1985, Integrating-averaging sound leve
44、l meters. IEC 804:1985/Amd.1:1989, Amendment No. 1. IEC 804:1985/Amd.2:1993, Amendment No. 2. 3 Definitions For the purposes of this International Standard, the following definitions apply. 3.1 transmission sound pressure level difference, D tps difference, in decibels, between the mean sound pressu
45、re levels on the source and receiver side of a silencer: where mean sound pressure levels are defined by where 3.2 insertion sound pressure level difference, D ips difference, in decibels, in sound pressure levels measured at a point or averaged over a small measurement area before and after install
46、ation of a silencer: where 3.3 transmission loss, D ts difference, in decibels, between the levels of the sound power incident upon and transmitted from the silencer: where .(1) is the mean sound pressure level (ref.204Pa), in decibels (in one-third-octave or octave bands, see IEC1260), on the recei
47、ver side of the silencer, for all measuring points used to determine the airborne sound within the duct or propagated from the aperture and external surfaces of the silencer; is the mean sound pressure level (ref.204Pa), in decibels (in one-third-octave or octave bands), on the source side of the si
48、lencer, for all measuring points used to determine the airborne sound reaching the silencer. NOTE 2D tpsis not self-standing but is an intermediate step towards determining the transmission loss (see9.1.3). D t ps L p2 L p1 = L p1 L p2 .(2) L pj is the individual level; N is the number of measuring
49、points. D ips= L pII L pI .(3) L pI is the sound pressure level (ref.20 4Pa), in decibels (in one-third-octave or octave bands, see IEC1260), of the sound source(s) measured at a point or averaged over a small measurement area, after installation of the silencer; L pII is the sound pressure level (ref.20 4Pa), 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. NOTE
