DIN EN ISO 3747:2011-03

This standard describes a method for determining the sound power level and sound energy level of a noise source using sound pressure. It is based on the comparison of the sound-pressure levels in octave frequency bands of the noise source under test with those of a calibrated reference sound source; A-weighted sound power levels or sound energy levels may then be calculated from the octave-band levels. The method can be applied where the noise source is generally mounted (in situ). It is therefore suitable for larger pieces of stationary equipment which, due to their manner of operation or installation, cannot readily be moved. This standard provides results either for accuracy grade 2 (engineering grade) or accuracy grade 3 (survey grade), depending on the extent to which the requirements concerning the test environment are met. Requirements are specified, amongst other things, for the test room, background noise, instrumentation, installation and operation of the noise source under test, recommendations for the location of the reference sound source and the location of the measurement points, and the measurements and calculations to be carried out. The annexes describe the calculation of an indicator to determine the suitability of the room or the accuracy to be achieved, and the calculation of sound power levels and sound energy levels under reference meteorological conditions and of A-weighted sound power levels from octave-band levels. Other annexes contain recommendations for the location of the reference sound source and the microphones for various emission patterns of the noise source under test and a guideline on the development of information on measurement uncertainty. The most important alterations with respect to the 2009 edition of the standard are as follows: a) determination of sound energy levels has been added; b) specifications for the mounting and fixing of the sound source under test have been added; c) treatment of measurement uncertainty has been extended and approach in accordance with the GUM Guide has been added; d) annex for the determination of sound power and sound energy levels under meteorological reference conditions has been added; e) annex with a guideline on the development of information on measurement uncertainty has been added; f) standard has been completely editorially revised. The international standard on which this standard is based has been prepared by Working Group 28 "Basic machinery noise emission standards" of ISO/TC 43/SC 1 "Noise" with German participation. On the European level, the standard exists within the framework of CEN/TC 211 "Acoustics". Regarding German cooperation, the responsible Working Committee is NA 001-01-04 AA "Geräuschemission von Maschinen und Anlagen: Messung, Minderung, Datensammlung" ("Noise emission of machines and plants: measurement, reduction, data collection") of NALS.