BS EN ISO 3744:2010

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Test environment
5 Instrumentation
6 Definition, location, installation, and operation
   of noise source under test
7 Reference box and measurement surface
8 Determination of sound power levels and sound
   energy levels
9 Measurement uncertainty
10 Information to be recorded
11 Test report
Annex A (normative) - Qualification procedures for
        the acoustic environment
Annex B (normative) - Microphone arrays on a
        hemispherical measurement surface
Annex C (normative) - Microphone arrays on a
        parallelepiped measurement surface
Annex D (informative) - Microphone arrays on a
        cylindrical measurement surface
Annex E (normative) - Calculation of A-weighted sound
        power levels and A-weighted sound
        energy levels from frequency band levels
Annex F (normative) - Alternative microphone array
        on a hemispherical measurement surface
        for direct measurements of A-weighted
        sound pressure levels
Annex G (normative) - Sound power level and sound
        energy level under reference meteorological
        conditions
Annex H (informative) - Guidelines on the development
        of information on measurement uncertainty
Bibliography
Annex ZA (informative) - Relationship between this
         European Standard and the Essential
         Requirements of EU Directive 2006/42/EC

Describes 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.

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).