Reference numberISO 3744:2010(E)©ISO 2010INTERNATIONAL STANDARD ISO3744Third edition2010-10-01Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure — Engineering methods for an essentially free field over a reflecting plane Acoustique — Détermination des niveaux de puissance et d énergie acoustiques émis par les sources de bruit à partir de la pression acoustique — Méthodes d expertise pour des conditions approchant celles du champ libre sur plan réfléchissant Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3744:2010(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe s licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobe s licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. COPYRIGHT PROTECTED DOCUMENT © ISO 2010 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO s member body in the country of the requester. ISO copyright office Case postale 56 • CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail
[email protected] Web www.iso.org Published in Switzerland ii © ISO 2010 – All rights reservedCopyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3744:2010(E) © ISO 2010 – All rights reserved iiiContents Page Foreword iv Introduction.v 1 Scope1 2 Normative references2 3 Terms and definitions .2 4 Test environment.8 5 Instrumentation .11 6 Definition, location, installation, and operation of noise source under test.12 7 Reference box and measurement surface14 8 Determination of sound power levels and sound energy levels 18 9 Measurement uncertainty.26 10 Information to be recorded.29 11 Test report31 Annex A (normative) Qualification procedures for the acoustic environment 32 Annex B (normative) Microphone arrays on a hemispherical measurement surface .37 Annex C (normative) Microphone arrays on a parallelepiped measurement surface .44 Annex D (informative) Microphone arrays on a cylindrical measurement surface55 Annex E (normative) Calculation of A-weighted sound power levels and A-weighted sound energy levels from frequency band levels59 Annex F (normative) Alternative microphone array on a hemispherical measurement surface for direct measurements of A-weighted sound pressure levels 61 Annex G (normative) Sound power level and sound energy level under reference meteorological conditions.64 Annex H (informative) Guidelines on the development of information on measurement uncertainty 66 Bibliography77 Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3744:2010(E) iv © ISO 2010 – All rights reservedForeword 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 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 the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. 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 least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 3744 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise. This third edition of ISO 3744 cancels and replaces the second edition (ISO 3744:1994) and ISO 4872:1978, of which it constitutes a merger and a technical revision. Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3744:2010(E) © ISO 2010 – All rights reserved vIntroduction This International Standard is one of the series ISO 3741[2]to ISO 3747[6], which specify various methods for determining the sound power levels and sound energy levels of noise sources including machinery, equipment and their sub-assemblies. General guidelines to assist in the selection are provided in ISO 3740[1]. The selection depends on the environment of the available test facility and on the precision of the sound power level or sound energy level values required. It may be necessary to establish a noise test code (see ISO 12001) for the individual noise source in order to select the appropriate sound measurement surface and microphone array from among those allowed in each member of the ISO 3741[2]to ISO 3747[6]series, and to give requirements on test unit mounting, loading and operating conditions under which the sound power levels or sound energy levels are to be obtained. The sound power emitted by a given source into the test environment is calculated from the mean square sound pressure that is measured over a hypothetical measurement surface enclosing the source, and the area of that surface. The sound energy for a single sound event is calculated from this sound power and the time over which it existed. The methods specified in this International Standard permit the determination of the sound power level and the sound energy level in frequency bands optionally with frequency A-weighting applied. For applications where greater accuracy is required, reference can be made to ISO 3745, ISO 3741[2]or ISO 9614[13]-[15]. If the relevant criteria for the measurement environment specified in this International Standard are not met, it might be possible to refer to another standard from this series, or to ISO 9614[13]-[15]. This International Standard describes methods of accuracy grade 2 (engineering grade) as defined in ISO 12001, when the measurements are performed in a space that approximates an acoustically free field over a reflecting plane. Such an environment can be found in a specially designed room, or within industrial buildings or outdoors. Ideally, the test source should be mounted on a sound-reflecting plane located in a large open space. For sources normally installed on the floor of machine rooms, corrections are defined to account for undesired reflections from nearby objects, walls and the ceiling, and for the residual background noises that occur there. Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---INTERNATIONAL STANDARD ISO 3744:2010(E)© ISO 2010 – All rights reserved 1Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure — Engineering methods for an essentially free field over a reflecting plane 1 Scope 1.1 General This International Standard specifies methods for determining the sound power level or sound energy level of a noise source from sound pressure levels measured on a surface enveloping the noise source (machinery or equipment) in an environment that approximates to an acoustic free field near one or more reflecting planes. The sound power level (or, in the case of noise bursts or transient noise emission, the sound energy level) produced by the noise source, in frequency bands or with A-weighting applied, is calculated using those measurements. NOTE Differently shaped measurement surfaces can yield differing estimates of the sound power level of a given noise source and an appropriately drafted noise test code (see ISO 12001) gives detailed information on the selection of the surface. 1.2 Types of noise and noise sources The methods specified in this International Standard are suitable for all types of noise (steady, non-steady, fluctuating, isolated bursts of sound energy, etc.) defined in ISO 12001. This International Standard is applicable to all types and sizes of noise source (e.g. stationary or slowly moving plant, installation, machine, component or sub-assembly), provided the conditions for the measurements can be met. NOTE It is possible that the conditions for measurements given in this International Standard are impracticable for very tall or very long sources such as chimneys, ducts, conveyors and multi-source industrial plants. A noise test code for the determination of noise emission of specific sources can provide alternative methods in such cases. 1.3 Test environment The test environments that are applicable for measurements made in accordance with this International Standard can be located indoors or outdoors, with one or more sound-reflecting planes present on or near which the noise source under test is mounted. The ideal environment is a completely open space with no bounding or reflecting surfaces other than the reflecting plane(s) (such as that provided by a qualified hemi-anechoic chamber), but procedures are given for applying corrections (within limits that are specified) in the case of environments that are less than ideal. 1.4 Measurement uncertainty Information is given on the uncertainty of the sound power levels and sound energy levels determined in accordance with this International Standard, for measurements made in limited bands of frequency and with frequency A-weighting applied. The uncertainty conforms to ISO 12001:1996, accuracy grade 2 (engineering grade). Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3744:2010(E) 2 © ISO 2010 – All rights reserved2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3382-2, Acoustics — Measurement of room acoustic parameters — Part 2: Reverberation time in ordinary rooms ISO 3745, Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure — Precision methods for anechoic test rooms and hemi- anechoic test rooms ISO 5725 (all parts), Accuracy (trueness and precision) of measurement methods and results ISO 6926, Acoustics — Requirements for the performance and calibration of reference sound sources for the determination of sound power levels ISO 12001:1996, Acoustics — Noise emitted by machinery and equipment — Rules for the drafting and presentation of a noise test code ISO/IEC Guide 98-3, Uncertainty in measurement — Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) IEC 60942:2003, Electroacoustics — Sound calibrators IEC 61260:1995, Electroacoustics — Octave-band and fractional-octave-band filters IEC 61672-1:2002, Electroacoustics — Sound level meters — Part 1: Specifications 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 sound pressure p difference between instantaneous pressure and static pressure NOTE 1 Adapted from ISO 80000-8:2007[21], 8-9.2. NOTE 2 Sound pressure is expressed in pascals. 3.2 sound pressure level Lpten times the logarithm to the base 10 of the ratio of the square of the sound pressure, p, to the square of a reference value, p0, expressed in decibels 22010 lg dBppLp= (1) where the reference value, p0, is 20 µPa [ISO/TR 25417:2007[20], 2.2] Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3744:2010(E) © ISO 2010 – All rights reserved 3NOTE 1 If specific frequency and time weightings as specified in IEC 61672-1 and/or specific frequency bands are applied, this is indicated by appropriate subscripts; e.g. LpAdenotes the A-weighted sound pressure level. NOTE 2 This definition is technically in accordance with ISO 80000-8:2007[21], 8-22. 3.3 time-averaged sound pressure level Lp,Tten times the logarithm to the base 10 of the ratio of the time average of the square of the sound pressure, p, during a stated time interval of duration, T (starting at t1and ending at t2), to the square of a reference value, p0, expressed in decibels 212,201()d10 lg dBttpTpttTLp⎡⎤⎢⎥=⎢⎥⎢⎥⎣⎦∫(2) where the reference value, p0, is 20 µPa NOTE 1 In general, the subscript “T” is omitted since time-averaged sound pressure levels are necessarily determined over a certain measurement time interval. NOTE 2 Time-averaged sound pressure levels are often A-weighted, in which case they are denoted by LpA,T, which is usually abbreviated to LpA. NOTE 3 Adapted from ISO/TR 25417:2007[20], 2.3. 3.4 single event time-integrated sound pressure level LEten times the logarithm to the base 10 of the ratio of the integral of the square of the sound pressure, p, of an isolated single sound event (burst of sound or transie
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