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 c = 400 N.s/m3 (where is the density of air and c is the speed ofsound). It specifies test room requirements, source location and general 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 International 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 International 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.