This part of ISO 4412 describes procedures for the determination of the sound power levels of a hydraulic fluid power pump, under controlled conditions of installation and operation, suitable for providing a basis for comparing the noise levels of pumps in terms of — A-weighted sound power level; — one-third octave band power level. From these sound power levels, if required, reference sound pressure levels may be calculated for reporting purposes (see clause 11). For general purposes, the frequency range of interest includes the one-third octave bands with centre frequencies between 100 Hz and 10 000 Hz.1) This part of ISO 4412 is applicable to all types of hydraulic fluid power pumps operating under steady-state conditions, irrespective of size, except for any limitations imposed by the size of the test environment (see clause 3).