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 ρc = 400 N.s/m3 (where ρ 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.