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ISO 3744:2025

Acoustics — Determination of sound power levels of noise sources using sound pressure — Engineering methods for an essentially free field over a reflecting plane

Edition date: 2025-12-11
In Force
Available languages: English, French
Summary:

1.1        General

This document specifies methods for determining the sound power 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 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 which are accounted for in the uncertainty associated with this test method. 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 document are suitable for all types of noise (steady, non-steady, and fluctuating) as defined in ISO 12001, except for short duration, impulsive events.

This document is applicable to all types and sizes of noise source (e.g. stationary or slowly moving component or sub-assembly), provided that the conditions for the measurements can be met.

NOTE   It is possible that the conditions for measurements given in this document 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 document 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. Annex A or ISO 26101-2 specifies methods for determining the adequacy of the test environment and for determination of corrections to be applied to account for the effect of the test environment.

1.4        Measurement uncertainty

Information is given on the uncertainty of the sound power levels determined in accordance with this document, for measurements made in limited bands of frequency and with frequency A-weighting applied. Annex I specifies procedures for testing laboratories that can be used to reduce measurement uncertainty. The uncertainty conforms to ISO 12001, accuracy grade 2 (engineering grade). General information on measurement uncertainty is provided in this document and additional information can be found in ISO 5114-1[8].



1.1        Généralités

Le présent document spécifie des méthodes de détermination du niveau de puissance acoustique émis par une source de bruit à partir des niveaux de pression acoustique mesurés sur une surface entourant la source de bruit (machine ou équipement), dans des conditions approchant celles du champ acoustique libre au voisinage d’un ou de plusieurs plans réfléchissants. Le niveau de puissance acoustique produit par la source de bruit, par bandes de fréquences ou avec la pondération A appliquée, est calculé en utilisant ces mesures.

NOTE   Des surfaces de mesure de formes différentes peuvent produire des estimations différentes du niveau de puissance acoustique d’une source de bruit donnée qui sont prises en compte dans l’incertitude associée à cette méthode d’essai. Un code d’essai acoustique rédigé de façon appropriée (voir l’ISO 12001) apporte des informations détaillées sur le choix de la surface.

1.2        Types de bruits et sources de bruit

Les méthodes spécifiées dans le présent document sont applicables à tous les types de bruit (stable, non stable, fluctuant) définis dans l’ISO 12001, à l’exception des événements impulsifs de courte durée.

Le présent document s’applique à tous les types de sources de bruit, quelles que soient leurs dimensions (par exemple composant ou sous-ensemble fixe ou se déplaçant lentement), sous réserve de pouvoir satisfaire les conditions de mesure.

NOTE   Dans le cas de sources particulièrement hautes ou longues (cheminées, conduits, convoyeurs, installations industrielles comprenant plusieurs sources), les conditions de mesure prescrites dans le présent document peuvent s’avérer impraticables. Dans ce cas, un code d’essai acoustique pour la détermination de l’émission sonore d’un type spécifique de sources peut fournir d’autres méthodes.

1.3        Environnement d’essai

Les environnements d’essai qui sont applicables aux mesurages réalisés conformément au présent document peuvent être en salle ou en plein air, comprendre un ou plusieurs plans acoustiques réfléchissants sur lesquels ou à proximité desquels est montée la source de bruit en essai. L’environnement idéal est un espace complètement libre, dépourvu de surfaces limites ou réfléchissantes autres que le ou les plans réfléchissants, tels que ceux d’une salle semi-anéchoïque qualifiée, mais des procédures sont fournies pour appliquer des corrections (dans des limites spécifiées) lorsque ces environnements ne correspondent pas à ces conditions idéales. L’Annexe A ou l’ISO 26101-2 spécifie des méthodes pour déterminer l’adéquation de l’environnement d’essai ainsi que les corrections à appliquer pour tenir compte de l’effet d’environnement.

1.4        Incertitude de mesure

Des informations sont données sur l’incertitude associée aux niveaux de puissance acoustique déterminés conformément au présent document pour des mesurages effectués dans des bandes de fréquences limitées et avec la pondération fréquentielle A. L’Annexe I spécifie les procédures destinées aux laboratoires d’essais qui peuvent être utilisées pour réduire l’incertitude de mesure. L’incertitude est conforme à celle de la classe de précision 2 (classe expertise) définie dans l’ISO 12001. Des informations générales sur l’incertitude de mesure sont fournies dans le présent document et des informations supplémentaires sont disponibles dans l’ISO 5114-1[8].
ICS: 17.140.01-Acoustic measurements and noise abatement in general
CTN: ISO/TC 43/SC 1 - 48474

Standards Cancellations

Anula a ISO 3744:2010

International Equivalence

Identic PNE-EN ISO 3744

Normas Conjuntas

Trabajo conjunto ISO 17631:2022

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