BS EN ISO 3740:2019 pdf download – Acoustics – Determination of sound power levels of noise sources – Guidelines for the use of basic standards
1 Scope
This document gives guidance for the use of a set of twelve basic International Standards (see Tables 1, 2 and 3) describing various methods for determining sound power levels from all types of machinery, equipment and products. It provides guidance on the selection of one or more of these standards, appropriate to any particular type of sound source, measurement environment and desired accuracy. The guidance given applies to airborne sound. It is for use in the preparation of noise test codes (see ISO 12001) and also in noise emission testing where no specific noise test code exists. Such standardized noise test codes can recommend the application of particular basic International Standard(s) and give detailed requirements on mounting and operating conditions for a particular family to which the machine under test belongs, in accordance with general principles given in the basic standards. This document is not intended to replace any of the details of, or add any additional requirements to, the individual test methods in the basic International Standards referenced. NOTE 1 Two quantities which complement each other can be used to describe the noise emission of machinery, equipment and products. One is the emission sound pressure level at a specified position and the other is the sound power level. The International Standards which describe the basic methods for determining emission sound pressure levels at work stations and at other specified positions are ISO 11200 to ISO 11205 (References [20] to [25]). NOTE 2 The sound energy level mentioned in ISO 3741 to ISO 3747 is not addressed in this document as it is not mentioned in any legal requirement. Its application is limited to very special cases of a single burst of sound energy or transient sound defined in ISO 12001.
In contrast to sound pressure measurements, sound intensity measurements used for determining the sound power level are less sensitive to steady state background noise and the environment, provided that the capacity of the measurement instrument is not exceeded. Background noise that fluctuates cyclically needs an adequately longer integration time at each measurement position. In principle, this measurement approach provides a measure of the sound power radiated directly into the air by all sources located within the enclosing surface, and excludes sound radiated by sources, including mirror sources resulting from sound reflections, located outside the enveloping surface. Owing to differences in meteorological conditions, sound power level measurements at different test facilities can yield considerably different results. For example, measurements of sound power level at high altitude cause an underestimate of the sound power level when compared to measurements at sea level. Therefore, many of the above mentioned measurement procedures except ISO 9614-1 and ISO 9614-2 include corrections to allow for any differences that can exist between the meteorological conditions under which the tests are conducted and reference meteorological conditions. ISO/TS 7849-1 and ISO/TS 7849-2 yield by definition the sound power level under reference meteorological conditions.