EN ISO 3747:2010

Acoustics - Determination of sound power levels and sound energy levels of noise sources using sound pressure - Engineering/survey methods for use in situ in a reverberant environment (ISO 3747:2010)

ISO 3747:2010 specifies a method for determining the sound power level or sound energy level of a noise source by comparing measured sound pressure levels emitted by a noise source (machinery or equipment) mounted in situ in a reverberant environment, with those from a calibrated reference sound source. 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 of width one octave, is calculated using those measurements. The sound power level or sound energy level with frequency A-weighting applied is calculated using the octave-band levels.
The method specified in ISO 3747:2010 is suitable for all types of noise (steady, non-steady, fluctuating, isolated bursts of sound energy, etc.) defined in ISO 12001. The method is primarily applicable to sources which emit broad-band noise. It can, however, also be used for sources which emit narrow-band noise or discrete tones, although there is a possiblity that the measurement reproducibility is then degraded.
The noise source under test can be a device, machine, component or sub-assembly, especially one which is non-movable.
The test environment that is applicable for measurements made in accordance with ISO 3747:2010 is a room where the sound pressure level at the microphone positions depends mainly on reflections from the room surfaces. In measurements of ISO 12001:1996, accuracy grade 2 (engineering grade), background noise in the test environment is low compared to that of the noise source or reference sound source.
Information is given on the uncertainty of the sound power levels and sound energy levels determined in accordance with ISO 3747:2010, for measurements made in octave bands and for A-weighted frequency calculations performed on them. The reproducibility conforms with that of either ISO 12001:1996, accuracy grade 2 (engineering grade) or ISO 12001:1996, accuracy grade 3 (survey grade), depending on the extent to which the requirements concerning the test environment are met.

Akustik - Bestimmung der Schallleistungs- und Schallenergiepegel von Geräuschquellen aus Schalldruckmessungen - Verfahren der Genauigkeitsklassen 2 und 3 zur Anwendung in situ in einer halligen Umgebung (ISO 3747:2010)

1.1 Allgemeines
Diese Internationale Norm legt ein Verfahren für die Bestimmung des Schallleistungs- oder Schallenergiepegels
einer Geräuschquelle fest, bei dem die von einer Geräuschquelle (Maschine oder Gerät) an
ihrem üblichen Aufstellungsort (in situ) erzeugten und in einer halligen Umgebung gemessenen Schalldruckpegel
mit denen von einer kalibrierten Vergleichsschallquelle verglichen werden. Der von der Geräuschquelle
erzeugte Schallleistungspegel (oder der Schallenergiepegel bei Impulsen oder anderen Geräuschen kurzer
Dauer) wird aus diesen Messungen in Oktavbändern berechnet. Der A-bewertete Schallleistungs- oder
Schallenergiepegel wird aus den Oktavbandpegeln berechnet.
1.2 Art der Geräusche und Geräuschquellen
Das in dieser Internationalen Norm festgelegte Verfahren ist für alle in ISO 12001 definierten Arten von
Geräuschen geeignet (gleichförmige, ungleichförmige, schwankende, Einzel-Schallimpulse usw.). Das
Verfahren ist vorrangig auf Quellen anwendbar, die ein breitbandiges Geräusch abstrahlen. Es darf jedoch
auch für Quellen benutzt werden, die ein schmalbandiges Geräusch oder Einzeltöne abstrahlen, obwohl dann
die Möglichkeit besteht, dass die Vergleichbarkeit der Messung herabgesetzt ist.
Die zu untersuchende Geräuschquelle kann ein Gerät, eine Maschine, Komponente oder Baugruppe sein,
insbesondere eine, die nicht fortbewegt werden kann.
1.3 Messumgebung
Die für Messungen nach dieser Internationalen Norm verwendbare Messumgebung ist ein Raum, in dem der
Schalldruckpegel an den Mikrofonpositionen hauptsächlich durch die Reflexionen an den Oberflächen des
Raumes bestimmt wird (siehe 4.1). Bei Messungen mit der Genauigkeitsklasse 2 nach ISO 12001:1996 muss
der Fremdgeräuschpegel in der Messumgebung notwendigerweise niedrig im Vergleich zu dem der
Geräuschquelle oder der Vergleichsschallquelle sein (siehe 4.2).

Acoustique - Détermination des niveaux de puissance acoustique et des niveaux d'énergie acoustique émis par les sources de bruit à partir de la pression acoustique - Méthode d'expertise et de contrôle pour une utilisation in situ en environnement réverbérant (ISO 3747:2010)

L'ISO 3747:2010 spécifie une méthode de détermination du niveau de puissance acoustique ou du niveau d'énergie acoustique d'une source de bruit en comparant les niveaux de pression acoustique mesurés émis par une source de bruit (machine ou équipement) montée in situ dans un environnement réverbérant, à ceux d'une source sonore de référence étalonnée. Le niveau de puissance acoustique (ou, dans le cas d'impulsions sonores ou d'émissions sonores transitoires, le niveau d'énergie acoustique) produit par la source de bruit, par bandes de fréquences d'une largeur égale à une octave, est calculé en utilisant ces mesurages. Le niveau de puissance acoustique ou le niveau d'énergie acoustique avec la pondération fréquentielle A appliquée sont calculés au moyen des niveaux par bande d'octave.
La méthode spécifiée dans l'ISO 3747:2010 est applicable à tous les types de bruit (stable, non stable, fluctuant, impulsions acoustiques isolées, etc.) définis dans l'ISO 12001. Elle s'applique principalement aux sources qui émettent un bruit à large bande. Cependant, elle peut également s'appliquer aux sources qui émettent un bruit à bande étroite ou des sons purs, bien que la reproductibilité du mesurage puisse s'en trouver réduite.
La source de bruit en essai peut être un dispositif, une machine, un composant ou un sous-ensemble, en particulier ceux ne pouvant pas être déplacés.
L'environnement d'essai applicable aux mesurages réalisés conformément à l'ISO 3747:2010 est une salle dans laquelle le niveau de pression acoustique aux différentes positions de microphone dépend principalement des réflexions par les surfaces de la salle. Dans les mesurages de classe de précision expertise (classe 2) telle que spécifiée dans l'ISO 12001:1996, le bruit de fond dans l'environnement d'essai est faible par comparaison avec celui de la source de bruit ou de la source sonore de référence.
Des informations sont données sur l'incertitude associée aux niveaux de puissance acoustique et aux niveaux d'énergie acoustique déterminés conformément à l'ISO 3747:2010, pour des mesurages effectués dans des bandes d'octave, ainsi que pour les niveaux pondérés A calculés à partir de ces mesures. La reproductibilité est conforme à la classe de précision expertise (classe 2) ou à la classe de précision contrôle (classe 3) telles que définies dans l'ISO 12001:1996, en fonction du degré de conformité aux exigences relatives à l'environnement d'essai.

Akustika - Določanje ravni zvočnih moči in in ravni zvočne energije virov hrupa z zvočnim tlakom - Inženirska/informativna metoda za uporabo na kraju samem (in situ) v odmevnem okolju (ISO 3747:2010)

Ta mednarodni standard opredeljuje metodo določanja ravni zvočnih moči ali ravni zvočne energije virov hrupa s primerjavo izmerjenih ravni zvočnih moči, ki jih oddaja vir hrupa (stroj ali oprema), nameščen na kraju samem v odmevnem okolju, s tistimi iz kalibriranega referenčnega vira hrupa. Raven moči zvoka (ali, v primeru prodorov hrupa ali prehodnih emisij hrupa, raven zvočne energije), ki jo proizvede vir hrupa v frekvenčnih pasovih širine ene oktave, je izračunana z uporabo teh merjenj. Raven moči zvoka ali raven energije zvoka, pri kateri je uporabljeno frekvenčno uteženje A, se izračuna z uporabo ravni oktavnega pasu.

General Information

• Status: Published
• Publication Date: 30-Nov-2010
• Withdrawal Date: 29-Jun-2011
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• ICS: 17.140.20 - Noise emitted by machines and equipment
• Technical Committee: CEN/TC 211 - Acuostics
• Drafting Committee: CEN/TC 211 - Acuostics
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 01-Dec-2010
• Due Date: 19-Jun-2010
• Completion Date: 01-Dec-2010
• Directive: 2006/42/EC - Directive 2006/42/EC of the European Parliament and of the Council of 17 May 2006 on machinery, and amending Directive 95/16/EC (recast)
• Directive: 98/37/EC - Machinery
• Mandate: M/396 - Mandate to CEN and Cenelec for standardisation in the field of machinery
• Mandate: M/BC/CEN/88/13 - Standardization request to CEN/CENELEC relating to machinery
• Ref Project: SIST EN ISO 3747:2011 - Acoustics - Determination of sound power levels and sound energy levels of noise sources using sound pressure - Engineering/survey methods for use in situ in a reverberant environment (ISO 3747:2010)

Relations

• Replaces: EN ISO 3747:2009 - Acoustics - Determination of sound power levels of noise sources using sound pressure - Comparison method in situ (ISO 3747:2000)
• Effective Date: 25-Dec-2010

Overview - EN ISO 3747:2010 (Acoustics, in situ reverberant methods)

EN ISO 3747:2010 (ISO 3747:2010) specifies an engineering/survey method for determining the sound power level and, for transient events, the sound energy level of noise sources using sound pressure measurements taken in situ in a reverberant environment. The procedure compares octave‑band sound pressure levels from the test source with those from a calibrated reference sound source to calculate one‑octave band sound power or sound energy. A‑weighted results are derived from the octave‑band data.

Key topics and technical requirements

• Measurement principle: comparison of measured sound pressure levels of the test source and a calibrated reference source in the same reverberant room.
• Frequency analysis: results reported in one‑octave bands; A‑weighted sound power/energy calculated from those bands.
• Types of noise covered: steady, non‑steady, fluctuating, isolated bursts and transient noise (suitable for broad‑band sources; can be used for narrow‑band or tonal sources though reproducibility may be degraded).
• Test environment: room where microphone levels are dominated by room reflections (reverberant conditions). For accuracy grade 2 (engineering grade), background noise must be low relative to the tested source.
• Instrumentation & standards: use of calibrated reference sound source and appropriate measurement equipment (microphones, filters and sound level meters) consistent with referenced standards.
• Uncertainty & reproducibility: guidance on estimation of measurement uncertainty; results conform to ISO 12001 accuracy grades 2 or 3 depending on compliance with environment requirements.
• Reporting: procedures define required information to record in the test report (measurement positions, environmental conditions, reference source data, calculation method).

Practical applications and who uses this standard

EN ISO 3747:2010 is used by:

• Acoustic and environmental consultants performing on‑site noise assessments
• Manufacturers and test laboratories measuring noise from large or non‑movable machines and installations
• R&D and product compliance teams verifying machine noise for design and regulatory conformity
• Health & safety and regulatory bodies assessing equipment noise where laboratory methods are impractical

Typical applications include noise evaluation of stationary industrial equipment, installed machinery, building services plant, and other in‑situ sources where a reverberant room measurement is practical.

Related standards

• ISO 3740 series (selection of sound power methods)
• ISO 12001 (noise test code drafting rules)
• ISO 6926 / IEC 60942 (reference sound source requirements)
• IEC 61260, IEC 61672 (filters and sound level meter performance)

Keywords: EN ISO 3747:2010, ISO 3747, sound power level, sound energy level, in situ acoustics, reverberant environment, octave bands, A‑weighting, reference sound source, measurement uncertainty.

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Akustik - Bestimmung der Schallleistungs- und Schallenergiepegel von Geräuschquellen aus Schalldruckmessungen - Verfahren der Genauigkeitsklassen 2 und 3 zur Anwendung in situ in einer halligen Umgebung (ISO 3747:2010)Acoustique - Détermination des niveaux de puissance acoustique et des niveaux d'énergie acoustique émis par les sources de bruit à partir de la pression acoustique - Méthode d'expertise et de contrôle pour une utilisation in situ en environnement réverbérant (ISO 3747:2010)Acoustics - Determination of sound power levels and sound energy levels of noise sources using sound pressure - Engineering/survey methods for use in situ in a reverberant environment (ISO 3747:2010)17.140.01Acoustic measurements and noise abatement in generalICS:Ta slovenski standard je istoveten z:EN ISO 3747:2010SIST EN ISO 3747:2011en01-marec-2011SIST EN ISO 3747:2011SLOVENSKI
STANDARDSIST EN ISO 3747:20091DGRPHãþD

EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN ISO 3747
December 2010 ICS 17.140.01 Supersedes EN ISO 3747:2009English Version
Acoustics - Determination of sound power levels and sound energy levels of noise sources using sound pressure - Engineering/survey methods for use in situ in a reverberant environment (ISO 3747:2010)
Acoustique - Détermination des niveaux de puissance acoustique et des niveaux d'énergie acoustique émis par les sources de bruit à partir de la pression acoustique - Méthode d'expertise et de contrôle pour une utilisation in situ en environnement réverbérant (ISO 3747:2010)
Akustik - Bestimmung der Schallleistungs- und Schallenergiepegel von Geräuschquellen aus Schalldruckmessungen - Verfahren der Genauigkeitsklassen 2 und 3 zur Anwendung in situ in einer halligen Umgebung (ISO 3747:2010) This European Standard was approved by CEN on 6 November 2010.
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 standards may be obtained on application to the CEN-CENELEC 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 responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2010 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 3747:2010: ESIST EN ISO 3747:2011

Relationship between this European Standard and the Essential Requirements of EU Directive 2006/42/EC .4 SIST EN ISO 3747:2011

Relationship between this European Standard and the Essential Requirements of EU Directive 2006/42/EC This European Standard has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association to provide a means of conforming to Essential Requirements of the New Approach Directive 2006/42/EC on machinery. Once this standard is cited in the Official Journal of the European Union under that Directive and has been implemented as a national standard in at least one Member State, compliance with the normative clauses of this standard confers, within the limits of the scope of this standard, a presumption of conformity with the corresponding Essential Requirements of that Directive and associated EFTA regulations. WARNING — Other requirements and other EU Directives may be applicable to the product(s) falling within the scope of this standard.
Reference numberISO 3747:2010(E)© ISO 2010
INTERNATIONAL STANDARD ISO3747Third edition2010-12-01Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure —Engineering/survey methods for use in situ in a reverberant environment Acoustique — Détermination des niveaux de puissance acoustique et des niveaux d'énergie acoustique émis par les sources de bruit à partir de la pression acoustique — Méthode d'expertise et de contrôle pour une utilisation in situ en environnement réverbérant
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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.
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ii © ISO 2010 – All rights reserved
ISO 3747:2010(E) © ISO 2010 – All rights reserved iii Contents Page Foreword.iv Introduction.v 1 Scope.1 2 Normative references.2 3 Terms and definitions.2 4 Test environment.6 5 Instrumentation and measurement equipment.6 6 Location, installation and operation of noise source under test.7 7 Measurement procedure.8 8 Calculation of sound power levels and sound energy levels.11 9 Measurement uncertainty.15 10 Information to be recorded.18 11 Test report.20 Annex A (normative)
Evaluation of the excess of sound pressure level at a given distance.21 Annex B (informative)
Recommendations for the location of the reference sound source and the microphones, if only one position is used for the reference sound source.22 Annex C (normative)
Sound power level and sound energy level under reference meteorological conditions.27 Annex D (normative)
Calculation of A-weighted sound power levels and A-weighted sound energy levels from octave-band levels.29 Annex E (informative)
Guidance on the development of information on measurement uncertainty.31 Bibliography.42
ISO 3747:2010(E) iv © ISO 2010 – All rights reserved 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 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 3747 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise. This third edition cancels and replaces the second edition (ISO 3747:2000), which has been technically revised. SIST EN ISO 3747:2011

ISO 3747:2010(E) © ISO 2010 – All rights reserved v Introduction This International Standard is one of the series ISO 3741[2] to ISO 3747, which specify various methods for determining the sound power levels and sound energy levels of noise sources including machinery, equipment and their sub-assemblies. The selection of one of the methods from the series for use in a particular application depends on the purpose of the test to determine the sound power level or sound energy level and on the facilities available. General guidelines to assist in the selection are provided in ISO 3740[1]. ISO 3740[1] to ISO 3747 give only general principles regarding the operating and mounting conditions of the machinery or equipment for the purposes of the test. It is important that test codes be established for individual kinds of noise source, in order to give detailed requirements for mounting, loading, and operating conditions under which the sound power levels or sound energy levels are to be obtained. The method given in this International Standard is based on a comparison of the sound pressure levels in octave frequency bands of a noise source under test with those of a calibrated reference sound source; A-weighted sound power levels or sound energy levels may be calculated from the octave-band levels. The method is applied where the noise source is found in situ and as such is suitable for larger pieces of stationary equipment which, due to their manner of operation or installation, cannot readily be moved. The method specified in this International Standard permits the determination of the sound power level and the sound energy level in octave bands from which the A-weighted value is calculated. This International Standard describes a method giving results of either ISO 12001:1996, accuracy grade 2 (engineering grade) or ISO 12001:1996, accuracy grade 3 (survey grade), depending on the extent to which the requirements concerning the test environment are met. For applications where greater accuracy is required, reference can be made to ISO 3741[2], ISO 3744[5] or an appropriate part of ISO 9614[17]-[19]. 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 an appropriate part of ISO 9614[17]-[19].
INTERNATIONAL STANDARD ISO 3747:2010(E) © ISO 2010 – All rights reserved 1 Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure — Engineering/survey methods for use in situ in a reverberant environment 1 Scope 1.1 General This International Standard specifies a method for determining the sound power level or sound energy level of a noise source by comparing measured sound pressure levels emitted by a noise source (machinery or equipment) mounted in situ in a reverberant environment, with those from a calibrated reference sound source. 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 of width one octave, is calculated using those measurements. The sound power level or sound energy level with frequency A-weighting applied is calculated using the octave-band levels. 1.2 Types of noise and noise sources The method specified in this International Standard is suitable for all types of noise (steady, non-steady, fluctuating, isolated bursts of sound energy, etc.) defined in ISO 12001. The method is primarily applicable to sources which emit broad-band noise. It can, however, also be used for sources which emit narrow-band noise or discrete tones, although there is a possibility that the measurement reproducibility is then degraded. The noise source under test can be a device, machine, component or sub-assembly, especially one which is non-movable. 1.3 Test environment The test environment that is applicable for measurements made in accordance with this International Standard is a room where the sound pressure level at the microphone positions depends mainly on reflections from the room surfaces (see 4.1). In measurements of ISO 12001:1996, accuracy grade 2 (engineering grade), background noise in the test environment is low compared to that of the noise source or reference sound source (see 4.2). 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 octave bands and for A-weighted frequency calculations performed on them. The uncertainty conforms with that of either ISO 12001:1996, accuracy grade 2 (engineering grade) or ISO 12001:1996, accuracy grade 3 (survey grade), depending on the extent to which the requirements concerning the test environment are met. SIST EN ISO 3747:2011

ISO 3747:2010(E) 2 © ISO 2010 – All rights reserved 2 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 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 used 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 of 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 definitions apply. 3.1 sound pressure p difference between instantaneous pressure and static pressure NOTE 1 Adapted from ISO 80000-8:2007[22], 8-9.2. NOTE 2 Sound pressure is expressed in pascals. 3.2 sound pressure level Lp ten 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: 22010lgdBppLp= (1) where the reference value, p0, is 20 µPa [ISO/TR 25417:2007[21], 2.2] NOTE 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. LpA denotes the A-weighted sound pressure level. NOTE 2 This definition is technically in accordance with ISO 80000-8:2007[22], 8-22. SIST EN ISO 3747:2011

ISO 3747:2010(E) © ISO 2010 – All rights reserved 3 3.3 time-averaged sound pressure level Lp,T ten 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 t1 and ending at t2), to the square of a reference value, p0, expressed in decibels 212,201()d10lgdBttpTpttTLp⎡⎤⎢⎥⎢⎥⎢=⎢⎢⎥⎢⎥⎢⎥⎣⎦∫⎥⎥ (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[21], 2.3. 3.4 single event time-integrated sound pressure level LE ten 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 transient sound) over a stated time interval T (starting at t1 and ending at t2) to a reference value, E0, expressed in decibels 2120()d10lgdBttEpttLE⎡⎤⎢⎥⎢⎥⎢⎥=⎢⎥⎢⎥⎢⎥⎢⎥⎣⎦∫ (3) where the reference value, E0, is (20 µPa)2 s = 4 × 10−10 Pa2 s NOTE 1 This quantity can be obtained by Lp,T + 10 lg(T /T0) dB, where T0 = 1 s. NOTE 2 When used to measure sound immission, this quantity is usually called “sound exposure level” (see ISO/TR 25417:2007[21]). 3.5 measurement time interval T portion or a multiple of an operational period or operational cycle of the noise source under test for which the time-averaged sound pressure level is determined NOTE Measurement time interval is expressed in seconds. 3.6 comparison method method by which the sound power level or sound energy level of a noise source under test is determined from a comparison of the sound pressure levels produced by the source under test with those of a reference sound source of known sound power output, when both sources are operated in the same environment SIST EN ISO 3747:2011

ISO 3747:2010(E) 4 © ISO 2010 – All rights reserved 3.7 reverberant sound field that portion of the sound field in the test room over which the influence of sound received directly from the source is negligible 3.8 reference sound source sound source meeting specified requirements NOTE For the purposes of this International Standard, the requirements are those specified in ISO 6926:1999, Clause 5. 3.9 calibration position position, well-defined relative to reflecting surfaces, in which the reference sound source has been calibrated 3.10 excess of sound pressure level at a given distance ΔLf difference, at a given distance, between the sound pressure level of a sound source in a given room and the sound pressure level that would be expected in a free sound field, expressed in decibels NOTE This term and its definition differ from that given in ISO 14257:2001[20], 3.6, which relates to an average difference over a given distance range. 3.11 frequency range of interest for general purposes, the frequency range of octave bands with nominal mid-band frequencies from 125 Hz to 8 000 Hz NOTE For special purposes, the frequency range can be extended or reduced, provided that the test environment, reference sound source, and instrument specifications are satisfactory for use over the modified frequency range. Any change to the frequency range of interest is clearly indicated in the test report. Measurements are not valid if the A-weighted levels are predominantly determined by high or low frequencies outside the frequency range of interest. 3.12 reference box hypothetical right parallelepiped terminating on the floor of the test environment on which the noise source under test is located, that just encloses the source including all the significant sound-radiating components and any test table on which the source is mounted 3.13 measurement distance dm distance from the nearest point of the reference box to a microphone position NOTE Measurement distance is expressed in metres. 3.14 background noise noise from all sources other than the noise source under test NOTE Background noise includes contributions from airborne sound, noise from structure-borne vibration, and electrical noise in the instrumentation. SIST EN ISO 3747:2011

ISO 3747:2010(E) © ISO 2010 – All rights reserved 5 3.15 background noise correction K1 correction applied to the measured octave-band sound pressure levels at each microphone position to account for the influence of background noise NOTE 1 Background noise correction is expressed in decibels. NOTE 2 The background noise correction is frequency dependent; the correction in the case of a frequency band is denoted K1f, where f denotes the relevant mid-band frequency. 3.16 sound power P through a surface, product of the sound pressure, p, and the component of the particle velocity, un, at a point on the surface in the direction normal to the surface, integrated over that surface [ISO 80000-8:2007[22], 8-16] NOTE 1 Sound power is expressed in watts. NOTE 2 The quantity relates to the rate per time at which airborne sound energy is radiated by a source. 3.17 sound power level LW ten times the logarithm to the base 10 of the ratio of the sound power of a source, P, to a reference value, P0, expressed in decibels 010lgdBWPLP= (4) where the reference value, P0, is 1 pW NOTE 1 If a specific frequency weighting as specified in IEC 61672-1 and/or specific frequency bands are applied, this should be indicated by appropriate subscripts; e.g. LWA denotes the A-weighted sound power level. NOTE 2 This definition is technically in accordance with ISO 80000-8:2007[22], 8-23. [ISO/TR 25417:2007[21], 2.9] 3.18 sound energy J integral of the sound power, P, over a stated time interval of duration T (starting at t1 and ending at t2)
21()dttJPtt=∫ (5) NOTE 1 Sound energy is expressed in joules. NOTE 2 The quantity is particularly relevant for non-stationary, intermittent sound events. [ISO/TR 25417:2007[21], 2.10] SIST EN ISO 3747:2011

ISO 3747:2010(E) 6 © ISO 2010 – All rights reserved 3.19 sound energy level LJ ten times the logarithm to the base 10 of the ratio of the sound energy, J, to a reference value, J0, expressed in decibels 010lgdBJJLJ= (6) where the reference value, J0, is 1 pJ NOTE If a specific frequency weighting as specified in IEC 61672-1 and/or specific frequency bands are applied, this should be indicated by appropriate subscripts; e.g. LJA denotes the A-weighted sound energy level. [ISO/TR 25417:2007[21], 2.11] 4 Test environment 4.1 Criterion for acoustic adequacy of test environment The test environment is where the noise source under test is found in situ, i.e. either where the source is built or where it normally operates. The method of test specified in this International Standard is for application in a reverberant sound field. The test environment shall therefore be sufficiently reverberant to cause the directivity of the source under test to have an insignificant influence on the sound pressure levels measured according to 7.5 and 7.6. The indicator, excess of sound pressure level at a given distance, ûLf, shall be determined in accordance with Annex A, and shall have a magnitude of at least 7 dB in regions where the requirement for a reverberant sound field is fulfilled. This indicator serves as the parameter by which to assess the measurement uncertainty, see Clause 9. 4.2 Criterion for background noise At each microphone position, the octave-band sound pressure levels due to background noise shall be at least 6 dB and preferably more than 15 dB below the octave-band sound pressure levels from the noise source under test and from the reference sound source. NOTE If it is necessary to make measurements where the difference between the sound pressure levels of the background noise and the sources is less than 6 dB, ISO 3746[7], ISO 9614-1[17] or ISO 9614-2[18] can be used. 5 Instrumentation and measurement equipment 5.1 General The instrumentation system, including the microphones and cables, shall meet the requirements of IEC 61672-1:2002, class 1, and the filters shall meet the requirements of IEC 61260:1995, class 1. The reference sound source shall meet the requirements given in ISO 6926. 5.2 Calibration Before and after each series of measurements, a sound calibrator meeting the requirements of IEC 60942:2003, class 1 shall be applied to each microphone to verify the calibration of the entire measurement system at one or more frequencies within the frequency range of interest. Without any adjustment, the difference between the readings before and after each series of measurements shall be less than or equal to 0,5 dB. If this value is exceeded, the results of the series of measurements shall be discarded. SIST EN ISO 3747:2011

ISO 3747:2010(E) © ISO 2010 – All rights reserved 7 The calibration of the sound calibrator, the compliance of the instrumentation system with the requirements of IEC 61672-1, and the compliance of the reference sound source with the requirements of ISO 6926, shall be verified at intervals in a laboratory making calibrations traceable to appropriate standards. Unless national regulations dictate otherwise, it is recommended that the sound calibrator should be calibrated at intervals not exceeding 1 year, the reference sound source should be calibrated at intervals not exceeding 2 years, and the compliance of the instrumentation system with the requirements of IEC 61672-1 should be verified at intervals not exceeding 2 years. 6 Location, installation and operation of noise source under test 6.1 Source location and installation Since the test procedure is designed for use in situ, the installation and location of the noise source under test have to be those where the source is found. However, the sound power or sound energy emitted by a source can be affected by the manner of installation and its location, for instance, relative to nearby walls or other reflecting surfaces.
Many small sound sources, although themselves poor radiators of low-frequency sound, can, as a result of the method of mounting, radiate more low-frequency sound when their vibrational energy is transmitted to surfaces large enough to be efficient radiators. In such cases, resilient mountings should if practicable be interposed between the noise source under test and the supporting structure, so that the transmission of vibration to the support and the reaction on the source are both minimized. In this case, the mounting base should be rigid (i.e. have a sufficiently high mechanical impedance) to prevent it from vibrating excessively and radiating sound. Such resilient mounts should not be used if the noise source under test is not resiliently mounted in typical usage. Coupling conditions, e.g. between prime movers and driven machines, can exert considerable influence on the sound radiation of the noise source under test. It may be appropriate to use a flexible coupling, but similar considerations apply to these as to resilient mounts. 6.2 Auxiliary equipment If practicable, all auxiliary equipment necessary for the operation of the noise source under test, but which is not an integral part of the source itself, including any electrical conduits, piping, air ducts, etc., connected to the source under test, shall be located outside the test environment. If this is impractical, care shall be taken to minimize any sound radiated into the test environment from such equipment. The noise source under test shall be taken to include all significant sources of sound emission, including auxiliary equipment which cannot either be removed or adequately quietened, and the reference box (see 7.2) shall be extended appropriately. 6.3 Operation of source during test The sound power or sound energy emitted by a source can be affected by the load applied, the running speed, and the conditions under which it is operating. The source shall be tested, wherever possible, under conditions that are reproducible and representative of the noisiest operation in typical usage. The specifications given in a noise test code, if any exists, shall be followed, but in the absence of a noise test code one or more of the following modes of operation shall be selected for the test(s): a) source under specified load and conditions; b) source under full load [if different from a)]; c) source under no load (idling); d) source at maximum operating speed under defined conditions; e) source operating under conditions corresponding to maximum sound generation representative of normal use; SIST EN ISO 3747:2011

ISO 3747:2010(E) 8 © ISO 2010 – All rights reserved f) source with simulated loading, under defined conditions; g) source undergoing a characteristic work cycle under defined conditions. The source shall be stabilized in the desired operating condition, with any power source or transmission system running at a stable temperature, prior to the start of measurements for sound power level or sound energy level determination. The load, speed, and operating conditions shall either be held constant during the test, or varied through a defined cycle in a controlled manner. If the sound power or sound energy emission depends on secondary operating parameters, e.g. the type of material being processed, the design of cutting tool, or the humidity, those parameters shall be selected, as far as is practicable, that give the smallest variations and that are typical of normal use. If simulated loading conditions are used, they shall be chosen such that the sound power levels or sound energy levels of the source under test are representative of normal use. 7 Measurement procedure 7.1 General For determination of either the sound power level of a noise source emitting stationary noise or the sound energy level of a source which emits bursts of noise, two sets of measurements of sound pressure levels shall be made in the test environment, first with the noise source under test operating and then with the reference sound source operating; in some circumstances (see 7.3.1) the measurements with the reference sound source have to be repeated for different locations of the source. The specifications given in a noise test code, if any exists, shall be followed, but in the absence of a noise test code the procedures described hereafter shall be followed for the test(s). 7.2 Characterization of noise source under test A preliminary aural examination of the noise emitted by the source under test shall be made to determine whether sound emitted from one component predominates. If so, the geometric centre of that component shall be assumed to be the acoustic centre of the source for the purpose of the test (see 7.3.2), and a reference box shall be delineated which just encloses that component and terminates on the floor on which the source under test is mounted. If no component appears to emit sound more than any other, any component which clearly emits no sound shall be excluded from consideration, the acoustic centre of the source shall be taken to be the geometric centre of the remainder, and the reference box shall be delineated accordingly. Preliminary measurements shall be used to determine whether the sound emitted by the source is too directional for the method of this International Standard to be applied. The source directivity shall be evaluated by measuring sound pressure levels of the source (at intervals of 2 m or less along a given side for a large source) at a distance of 1 m from the reference box and a height normally of 1,5 m. If the source emits sound predominantly in an upward direction, the height at which the sound pressure levels are measured shall be sufficient to ensure that the microphone positions are in a direct line of sight to the acoustic centre of the source. If the A-weighted range of sound pressure levels so measured varies by no more than ±2 dB, the source shall be considered to be omnidirectional; if the variations exceed this amount, the source shall be considered to be directional. If the range of these directivity measurements exceeds ±7 dB, the engineering grade limits on source directivity are exceeded and the reported grade of accuracy shall not exceed that of ISO 12001:1996, accuracy grade 3 (survey grade) (see Clause 9). 7.3 Locations of the reference sound source 7.3.1 General Normally, one location for the reference sound source is sufficient. For noise sources under test which are large or which have two or more clearly distinguishable sound sources far apart from one another, two or more locations may need to be used (see 7.3.3). SIST EN ISO 3747:2011

ISO 3747:2010(E) © ISO 2010 – All rights reserved 9 7.3.2 One location If one location is sufficient, the reference sound source shall be positioned as close as possible to the acoustic centre of the noise source under test. For a directional source, the reference sound source should be located to simulate the emission pattern of the noise source under test or, if this is impractical, a position for the reference sound source on top of the source under test shall be chosen. If this is not possible, a location shall be selected alongside the source under test, at a height and position which best simulate the emission pattern of the source under test. In the latter case, positions closer than 0,5 m to the surface of the reference box should be avoided. For an omnidirectional source under test, care shall be taken to ensure that the reference sound source can emit sound equally in all directions. NOTE 1 The more reverberant the test environment is, in other words, the larger ΔLf is, the less critical is the selection of the location for the reference sound source. However, if a position is selected for the reference sound source for which it is not calibrated, the reproducibility of the sound power level or sound energy level determined is degraded, see Clause 9. NOTE 2 Each reflecting surface within λ/2 (half a wavelength) of the reference sound source can increase its sound power, resulting in a possible underestimate of the noise source sound power level of up to 3 dB. Conversely, placing the reference sound source less than 0,5 m from the edge or edges of the reflecting floor plane can reduce its sound power output below 400 Hz, resulting in a possible overestimate of the noise source sound power level of up to 3 dB. NOTE 3 Further guidance on selection of the location for the reference sound source is given in Annex B. 7.3.3 More than one location The number of locations required for the reference sound source depends on the ratio a/dm, where a is the largest dimension of the reference box and dm is the measurement distance, see 7.4.1. The number of locations to be used is specified in a) to c). a) If a/dm >1 and if the source under test is omnidirectional, several locations shall be used for the reference sound source along the sides of the source under test, separated by a distance equal to dm. b) If a/dm >1 and if the source under test has clearly definable sound emission areas, one location of the reference sound source shall be used for each emission area. c) If a/dm u1 and if the source under test is omnidirectional, but it is impossible to use a location on top of the source under test, four locations for the reference sound source shall be used, one adjacent to each vertical side of the reference box. 7.4 Microphone positions 7.4.1 General The aim is to position the microphones around the sides of the noise source under test so that each position is situated similarly in relation to the sound-emitting areas of the source, i.e. for a particular microphone position, either there is a line of sight to each sound-emitting area or each area is screened. Positions to be avoided are those to which only a few parts of the source are emitting sound. In total, three or four microphone positions are to be used (see 7.4.3), distributed as evenly as possible around the noise source under test. The same positions and microphone orientations are to be used for measurements made on the noise source under test, the reference sound source, and the background noise. The measurement distance, dm, from the respective microphone positions to the nearest point of the reference box is to be selected so that, if possible, the microphone positions are in a part of the test environment where the sound field is reverberant, i.e. a region in which ΔLf W 7 dB (see Table 2). No microphone position shall be closer than 0,5 m to any boundary surface of the test environment. If the environment is sufficiently spacious, and if the noise source under test is located away from all boundary surfaces, the microphones shall be positioned round all four vertical sides of the reference box. The microphone positions shall be spaced at least 2 m from each other. If the ceiling is high and sound absorbing, and frequencies greater than 2 000 Hz are important, if possible, at least two of the microphone positions shall be above the source. SIST EN ISO 3747:2011

ISO 3747:2010(E) 10 © ISO 2010 – All rights reserved 7.4.2 Zoning The test environment shall be divided into zones in which differences can be denoted in the sound-radiating patterns in the horizontal plane around the noise source under test (ST) and the reference sound source (RSS) in its various locations. The zones are used in choosing locations for the reference sound source and the microphone positions. The different zones are identified and given notations in Table 1. Table 1 — Zones of the test environment Direct line of sight to sound-emitting areas Distances from the microphone position of ST of RSS dm a Effect on the sound power estimation Notation of the zone Yes No — Strong overestimate ++ No Yes — Strong underestimate −=Yes Yes dm(ST) < dm(RSS) Overestimate + Yes Yes dm(ST) > dm(RSS) Underestimate − Yes Yes dm(ST) ≈ dm(RSS) (within 10 %) Negligible over- or underestimate +/− No No — Either strong over- or underestimate ++/− a (ST) indicates source under test; (RSS) indicates reference sound source.
7.4.3 Selection of microphone positions If the noise source under test is omnidirectional and the reference sound source is located on top of it, all the zones fall into one or other of the notations + or +/− and one microphone position shall be selected on each free side of the source under test, in compliance with the requirements of 7.4.1. In all other cases, microphone positions shall be sought in a +/− zone. If this is not possible, one microphone position shall be selected in a + zone, one in a +/− zone and one or two positions in − zones. Unless the test environment is highly reverberant (no acoustic treatment of walls or ceiling, no large absorbing obstacles) no microphone positions should be located in a ++/− zone. NOTE
It can prove impossible to have all microphone positions in direct line of sight of the reference sound source (see B.2 and B.4). 7.5 Measurement of sound pressure levels for a noise source which emits steady or non-steady noise Time-averaged sound pressure levels from the noise source under test, for each octave band within the frequency range of interest, L′pi(ST), shall be obtained, at each microphone position, i (i = 1, 2 … n), and from the reference sound source, L′pi(RSS). A suitable averaging time for the reference sound source is 30 s. If the sound output from the noise source under test is as stable as that of the reference sound source, then a similar averaging time is satisfactory, but if it is less stable or undergoes periodic cycles, a longer averaging time is required. In addition, either immediately before or immediately after the sound pressure levels from the noise source under test are measured, the time-averaged sound pressure levels of the background noise for each octave band, Lpi(B), shall be obtained at each microphone position, over the same measurement time interval as that used for the noise source under test. SIST EN ISO 3747:2011

ISO 3747:2010(E) © ISO 2010 – All rights reserved 11 7.6 Measurement of sound pressure levels for a noise source which emits impulsive noise Single event sound pressure levels from the noise source under test for each octave band within the frequency range of interest, L′Ei(ST), shall be obtained, at each microphone position, i (i = 1, 2 … n), either for one single sound event at a time (in which case the process shall be repeated N times, where N W 5), or from several successive, N, sound events (where again N W 5). The measurement time interval shall be long enough to contain all that part of the noise of the event(s), including the decay, which make a significant contribution to the single event sound pressure level. The time-averaged sound pressure levels from the reference sound source, L′pi(RSS), shall also be measured, with an averaging time of 30 s. In addition, either immediately before or immediately after the sound pressure levels from the noise source under test are measured, the time-averaged octave-band sound pressure levels of the background noise, Lpi(B), shall be obtained once at each microphone pos
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