UL 51:2002 pdf download Acoustics — Determination of sound power levels of noise sources using sound pressure — Precision method for reverberation rooms
1 Scope
1.1 This International Standard specifies a direct method and a comparison method for determining the soundpower level that would be produced by a source operating in an environment at standard meteorological conditionscorresponding to a characteristic impedance of pc = 400 N-s/m3 (where p is the density of air and c is the speed oisound). t specifies test room requirements, source location and genera rules for operating conditions.instrumentation and techniques for obtaining an estimate of mean-square sound pressure levels from which thesound power levels of the source in octave or one-third-octave bands are calculated with a grade 1 accuracy. Thequantities to be measured are time-averaged sound pressure levels in frequency bands, The quantities to bedetermined are sound power levels, A-weighted and in frequency bands. Other quantities, which are optional, aresound power levels with other frequency weightings calculated from the measurements in frequency bands. Thisstandard does not provide the means to determine directivity and temporal variation of sound from a source.
In general, the frequency range of interest includes the one-third-octave bands with midband frequencies from100 Hz to 10 000 Hz. Guidelines for the application of the specified methods in an extended frequency range inrespect to lower frequencies are given in annex C. This nternational Standard is not applicable to frequency rangesabove the 10 000 Hz one-third-octave band. For higher frequencies the use of methods given in ISO 9295 isrecommended.
1.2 The method specified in this lnternational Standard is suitable for steady noise with broad-band, narrow-bandand discrete-frequency components as described in ISO 12001. The noise may be emitted from a device, machine,component or sub-assembly.
This international Standard is applicable to noise sources with volumes which are preferably not greater than 2 % ofthe volume of the reverberation room used for the test, For sources with volumes greater than 2 % of the roomvolume, the standard deviations given by Table 2 could be exceeded.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions otthis international Standard. For dated references, subsequent amendments to, or revisions of, any of thesepublications do not apply. However, parties to agreements based on this International Standard are encouraged toinvestigate the possibility of applying the most recent editions of the normative documents indicated below. Forundated reterences, the latest edition of the normative document referred to applies. Members of ISO and IECmaintain registers of currently valid internationa Standards.
ISO 354, Acoustics — Measurement of sound absorption in a reverberation room.
ISO 4871, Acoustics 一 Declaration and verification of noise emission values of machinery and equipment.ISO 6926, Acoustics — Determination of sound power lvels of noise sources 一- Requirements for the performanceand calibration of reference sound sources.
ISO 7574-1:1985,Acoustics — Statistical methods for determining and verifying stated noise emission values ofmachinery and equipment – Part 1: General considerations and definitions.