BS EN ISO 3740:2019 pdf free.Acoustics – Determination of sound power levels of noise sources – Guidelines for the use of basic standards.
3.1 emission <acoustics> airborne sound radiated by a well-defined noise source (e.g. the machine under test) under specified operating and mounting conditions Note 1 to entry: Emission values may be incorporated into a product noise declaration, product label and/or product specification. The basic noise emission quantities are the sound power level of the source itself and the emission sound pressure levels at the work station and/or at other specified positions (if any) in the vicinity of the source. [SOURCE: ISO 12001:1996, 3.3, modified – Note 1 to entry “product noise declaration” added.]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.Sound power levels determined according to different methods include different random and systematic deviations. Random deviations are clearly dealt with in the present sound power measurement standards but systematic ones are not addressed.BS EN ISO 3740 pdf download.