DIN EN ISO 3741:2011-01

This standard describes methods of accuracy grade (precision grade) for determining the sound power level and sound energy level of a noise source (machinery or equipment) from sound pressure measurements. For this purpose, the noise source under test shall be mounted in a reverberation test room having specified acoustical characteristics. The measurements are carried out in one-third-octave band widths. The sound power and sound energy levels can be determined using the equivalent absorption area of the room (direct method) or the reference sound source (comparison method). Requirements are specified, amongst other things, for the test room, background noise, meteorological environmental conditions, instrumentation and installation and operation of the noise source under test. The annexes describe the reverberation test room qualification procedure for the measurement of broad- and narrow-band noises, for the extension of the usable frequency range to lower frequencies (below 100 Hz), for the calculation of octave-band- and A-weighted levels from one-third-octave values and information for the design of reverberation test rooms and rotating diffusers are given. Another annex contains 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) criteria and application of background noise correction have been specified more precisely; b) absolute criterion for background noise has been additionally added; c) meteorological correction has been revised; d) determination of sound energy levels has been added; e) treatment of measurement uncertainty has been extended and approach in accordance with the GUM Guide has been added; f) reverberation test room qualification procedure at lower frequencies has been expanded; g) annex with a guideline on the development of information on measurement uncertainty has been added; h) 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.