1、STD-BSI BS EN ISO/TR LLb8-2-ENGL 2001 88 Lb24bL- BRITISH STANDARD Acoustics - Recommended practice for the design of low-noise machinery and equipment - Part 2: Introduction to the physics of low-noise design The European Standard EN IS0 116882:2000 has the status of a British Standard ICs 17.140.20
2、; 21.020 0895164 T84 BS EN ISO/TR 11688-2:2001 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW STD-BSI BS EN IS/TR LLbB-Z-ENGL 2001 W Lb24bb7 0895365 BS EN ISORa 11688-2:2001 been prepared under the direction of the Health and Environment Sector Committee, was published under
3、the authority of the Standards Committee and comes inta effect on 15 March 2001 Amd. No. Q BSI 03-2001 ISBN O 680 35696 7 National foreword Date Comments This British Standard is the English language version of EN ISOR 1168822000. It is identical with ISOR 116882 1998. The UK participation in its pr
4、eparation was entrusted by Technical Committee Ewl, Acoustics, to Subcommittee EWl4, Machinew noise, which has the responsibility to: - aid enquirers to understand the te - present to the responsible intedomUEuropean committee any enquiries on the interpretation, or proposals for change, and keep th
5、e UK interests - monitor related intedonal and European developments and promulgate iIlfOIlll 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 i
6、nclude an annex which lists normative references to international publications with their corresponding European publications. The British Stan* which implement these international or European publications may be found in the BI Standards Catalogue under the section entitled “Intemational Standards
7、Correspondence Index”, or by using the “Find“ facility of the BSI Standards Ele 21.020 English version Acoustics - Recommended practice for the design of low-noise machinery and equipment - Part 2: Introduction to the physics of low-noise design (ISOTTR 1 1 688-2: 1998) Acoustique - Pratique recomma
8、nde pour la conception de machines et quipements bruit rduit - Partie 2: Introduction la physique de la conception bruit rduit (ISO/TR 11688-2:1998) Akustik - Richtlinien fr die Gestaltung Irmarmer Maschinen und Gerte - Teil 2: Einfhrung in die Physik der Lrmminderung durch konstruktive Manahmen (IS
9、OTTR 1 1688-2:1998) This European Standard was approved by CEN on 17 September 1999. CEN members are bound to comply with the CEWCENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists an
10、d bibliographical references concerning such national standards may be obtained on application to the Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibili
11、ty of a CEN member into its own language and notified to the Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands,
12、 Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN C0MMITE.E FOR STANDARDIZATION COMITI? EUROPEEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Stassart, 36 8-1050 Brussels 8 2000 CEN All rights of exploitation in any form and by any means reserved
13、 worldwide for CEN national Members. Ref. No. EN IS0 11 688-2;2000 E STD-BSI BS EN ISOITR LLb8-2-ENGL 2OOL U Lb24bb3 08353b7 773 6 EN IS0 11688-22000 Foreword The text of the International Standard from Technical Committee ISO/TC 43 “Acoustics“ of the International Organization for Standardization (
14、ISO) has been taken over as an European Standard by Technical Committee CEN/TC 21 1 “Akustik“, 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 or by endorsement, at the latest by 2001, and con
15、flicting national standards shall be withdrawn at the latest by June 2001. This European Standard has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s). According to the CENICENELEC In
16、ternal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerla
17、nd and the United Kingdom. Endorsement notice The text of the International Standard ISO/TR 11688-2:1998 has been approved by CEN as a European Standard without any modification. STDaBSI BS EN ISO/TR LLbBd-Z-ENGL ZODl Lb24669 0895Lb8 b2T 0 EN IS0 11688-2:2000 TECHNICAL ISO/TR REPORT 11 688-2 First e
18、dition 1998-09-01 Acoustics - Recommended practice for the design of low-noise machinery and equipment - Part 2: Introduction to the physics of low-noise design Acoustique - Pratique recommande pour la conception de machines et quipements bruit rduit - Partie 2: Introduction la physique de la concep
19、tion 2 bruit rduit Reference number ISO/TR 11688-2:1998(E) Contents 1 Scope . 2 References . 3 Definitions . 4 Acoustical modelling 5 Control of airborne and liquid-borne noise 5.1 Generation of fluid-dynamic noise . 5.2 Noise control measures 6 Control of structure-borne sound . 6.1 Model of sound
20、generation . 6.2 Internal sources . 6.3 Transmission of structure-borne sound . 6.4 Control of structure-borne sound transmission by damping . 6.5 Radiation . 7 Analysis by measurement methods . 7.1 Purpose of the analysis . 7.2 Internal sources . 7.3 Transmission paths . 7.4 Radiation . 7.5 Summary
21、 of procedures for the analysis of existing 8 8.1 Purpose of the analysis . 8.2 Deterministic methods 8.3 Statistical methods 8.4 Applicability of computational methods . Annex A Example of the estimation of airborne sound emission of a machine caused by structure-borne and airborne sound emission f
22、rom a component Annex B Glossary machinery by measurement methods . Analysis by computational methods Bibliography 1 1 1 1 2 2 8 10 10 15 18 28 30 35 35 36 36 36 37 39 39 39 39 39 41 44 46 ii STD-BSI BS EN ISO/TR LLhflB-Z-ENGL 2002 E Lb24bb9 0875370 288 EN IS0 11688-22000 Foreword IS0 (the Internati
23、onal Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body interested in a subject for which a technical committee has been
24、 established has the right to be represented on that committee. International organisations, governmental and non- governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical stand
25、ardization. The main task of technical committees is to prepare International Standards, but in exceptional circumstances a technical cornmittee may propose the publication of a Technical Report of one of the following types: type 1, when the required support cannot be obtained for the publication o
26、f an International Standard, despite repeated eff Orts; type 2, when the subject is still under technical development or where for any other reason there is the future but not immediate possibility of an agreement on an International Standard; type 3, when a technical committee has collected data of
27、 a different kind from that which is normally published as an International Standard (“state of the art“, for example) Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether they can be transformed into International Standards. Technical Reports
28、 of type 3 do not necessarily have to be reviewed until the data they provide are considered to be no longer valid or useful. ISOifR 11688-2, which is a Technical Report of type 3, was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise. IS0 11 688 consists of the followin
29、g parts, under the general title Acoustics - Recommended practice for the design of low-noise machinery and equipment - Pari I: Planning - Pari 2: Introduction to the physics of low-noise design iii STD.BSI BS EN ISO/TR 1lb8-2-ENGL 2001 3624bb 0895171 114 EN IS0 11688-2:2000 I nt rod ucti on The obj
30、ective of this part of ICOTTR 11688 is noise reduction in existing machinery and noise control at the design stage of new machinery. It is important that non-acoustic engineers are engaged in noise control practice. It is of great importance for these engineers to have a basic knowledge of noise gen
31、eration and propagation characteristics and to understand the principles of noise control measures. iv STDUBS1 BS EN ISO/TR Llb88-2-ENGL 2001 Lb24667 0895172 O50 6 EN IS0 11688-2:2000 Acoustics - Recommended practice for the design of low-noise machinery and equipment - Part 2: Introduction to the p
32、hysics of low-noise design 1 Scope This part of ISOTTR 11688 provides the physical background for the low-noise design rules and examples given in ISOTTR 11688-1 and supports the use of extensive special literature. It is intended for use by designers of machinery and equipment as well as users and/
33、or buyers of machines and authorities in the field of legislation, supervision or inspection. Equations given in this Technical Report will improve the general understanding of noise control. In many cases they allow a comparison of different versions of design, but they are not useful for the predi
34、ction of absolute noise emission values. Information on internal sound sources, transmission paths and sound radiating parts of a machine is the basis for noise control in machines. Therefore measurement methods and computational methods suitable to obtain this information are described in clauses 7
35、 and 8 and annex A. 2 References See ISOTR 11688-1 and the bibliography. 3 Definitions See ISO/TR 11688-1 and annex A. 4 Acoustical modelling In order to facilitate the understanding of complex sound generation and propagation mechanisms in machinery and equipment or vehicles (the latter are also ca
36、lled “machines“ in this part of ISOTTR 11688), it is necessary to create simple acoustical models. The models provide a basis for noise control measures at the design stage. ISOTTR 11688-1:1995, Acoustics - Recommendedpractice for the design of low-noise machinery and equipment - Part 7: Planning. 1
37、 STD-BSI BS EN ISO/TR LLbBB-Z-ENGL 2001 H 2b24b69 0895273 T97 111 EN IS0 11688-2:2000 A universal approach is to distinguish between - internal sources; - transmission paths inside the machine; - radiation from its boundaries. The internal sources and the transmission paths can each be assigned to t
38、hree categories according to the media used: - airborne; - liquid-borne; - structure-borne. Radiation is considered for air only. Figures 1 and 2 serve to illustrate the principle of acoustical modelling. Figure 1 shows a simplified machine consisting of an electric motor and a housing with an openi
39、ng in it. The motor is the only internal source. It generates airborne and structure-borne sound. There are three internal transmission paths: - through the air inside the housing to the opening; - through the air inside the housing to the walls of the housing; - through the fastenings to the walls
40、of the housing. Radiation occurs from the opening and from the walls of the housing. Figure 2 illustrates this in a block diagram. The total sound power emitted from the machine is the sum of the three contributions. A systematic approach starts with an assessment of the relative importance of these
41、 contributions. The next step is examining the blocks in Figure 2 looking for possibilities to reduce source strength, transmission and/or radiation (see also following clauses). This should be done in relation to the various aspects of the design process (see ISOTTR 1 1688-1 :1995, Figure 1). 5 Con
42、trol of airborne and liquid-borne noise The basic principles of generation, transmission and radiation of sound in air (or other gases) and liquids are basically identical and are therefore considered together in this clause. There is only one important exception: cavitation. Occurring in liquids on
43、ly, this phenomenon is considered separately in 5.1.3. 5.1 Generation of fluid-dynamic noise Important noise-generating phenomena in gases and liquids are turbulence, pulsation and shock. Fluid-dynamic processes generate noise if flow rate and pressure vary over time in a limited volume of a liquid
44、or a gas, for example in a turbulent flow. This leads to the transmission of sound from the disturbed volume of the fluid to the surrounding medium. A classic example of this is the escape of compressed air from a nozzle. 2 STDaBSI BS EN ISO/TR llb88-2-ENGL 2001 U 1624667 0875L74 923 EN IS0 11688-22
45、000 Radiation of airborne sound from the opening Radiation of airborne sound from the housing -= Transmission of structure-borne -sound to the housing -Motor Fastening Figure 1 - Simplified machine for the illustration of acoustical modelling Radiation from opening Airborne sound Radiation from hous
46、ing Radiation from housing Motor Figure 2 - Block diagram for the illustration of generation, transmission and radiation of sound in the “machine“ of Figure 1 Mechanisms of fluid-dynamic sound generation can be related to properties of elementary sound sources with known characteristics: - monopoles
47、; - dipoles; - quadrupoles. 5.1.1 Elementary model sources A monopole source is an in-phase volume change, such as a pulsating volume of any shape or a piston in a large rigid surface. In the far field, monopoles have a spherical radiation pattern. The sound radiated from a monopole source can be re
48、duced by reducing the temporal variation in the volume flow rate. EXAMPLE 1 : Outlets of internal combustion engines, rotary piston fans, multi-cell compressors, piston pumps, piston compressors, flares. A dipole source arises as a result of external time-variable forces acting on a fluid without vo
49、lume change, such as in an oscillating rigid body of any shape. The dipole source can be replaced by two monopole sources of equal strength and opposite phase situated very closely together. The far-field directivity pattern of a dipole is shown in Table 1. Radiation from a dipole can be reduced by reducing the temporal variation of the forces acting on the fluid. EXAMPLE 2: Vibrating rigid parts of machinery, parts of machinery running out of balance, ducts, propellers and fans. A auadruDole source can be represented by a time-variable defor
