DIN EN ISO 3745:2012-07

This standard specifies methods for measuring the sound power levels and sound energy levels of noise sources. For this purpose, the noise source (machinery or equipment) under test is mounted either in a free-field test room or hemi-free-field test room (anechoic room or hemi-anechoic room) and sound pressure levels (in one-third octave bands or with frequency weighting A) and measured on a measurement surface enveloping the noise source. The calculated sound power levels and sound energy levels include corrections to allow for any differences that might exist between the meteorological conditions under which the tests are conducted and reference meteorological conditions. In general, the frequency range of interest includes the one-third-octave bands with mid-band frequencies from 100 Hz to 10 000 Hz. The range can be extended or restricted to frequencies beyond or within these limits, to those between which the test room is qualified for the purposes of these measurements. The specified methods are suitable for all types of noise (steady, non-steady, fluctuating) according to DIN EN ISO 12001. The noise source under test can be a device, machine, component or sub-assembly. The maximum size of the noise source depends on specified requirements regarding the radius of the hypothetical sphere or hemisphere used as the enveloping measurement surface. The test rooms that are applicable for measurements made in accordance with this standard are an anechoic room or hemi-anechoic room, also called, respectively, a free-field test room or hemi-free-field test room. Information and further details are given on the uncertainty of the sound power levels and sound energy levels determined in accordance with this standard. The most important alterations with regard to the 2009 edition of the standard are: a) terms and definitions have been extended; b) criteria for background noise have been extended and specifications relating to absolute criteria have been included; c) specifications relating to the calibration and verification of the measuring instruments have been supplemented; d) the air absorption is now taken into account when determining sound power levels and sound energy levels; e) specifications relating to the measurement uncertainty including the annex on the development of information on measurement uncertainty have been revised; f) Figure of microphone positions on the spherical surface for test sound source directivity measurements has been included in Annex A; g) the calculation of A-weighted levels from one-third-octave band levels has been supplemented by sound energy levels (Annex C); h) the specifications relating to the additional microphone positions (21 to 40) for measurements in a free field have been modified and a corresponding figure has been included (Annex D); i) the microphone position for measurements in a hemi-free field (general case) has been partly modified (Table E.1, Figure E.1); the previous microphone position now applies only to broadband omnidirectional sources (Table E.2, Figure E.2); j) annex with guidelines for the design of test rooms has been deleted; k) the standard has been completely editorially revised. The underlying standard has been prepared by Working Group 28 "Basic machinery noise emission standards" of ISO/TC 43/SC1 "Noise" with the German collaboration. On the European level, the standard is under the responsibility of CEN/TC 211 "Acoustics". Regarding the German collaboration, the responsible committee is Working Committee NA 001-01-04 AA "Geräuschemission von Maschinen und Anlagen: Messung, Minderung, Datensammlung" ("Noise emission of machines and plants: measurement, reduction, data collection").