ISO 4412-3:1991 pdf download.Hydraulic fluid power一Test code for determination of airborne noise levels
I Scope
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 10000 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).
2 NormatIve references
The following standards contain provisions which, through reference In this text, constitute provisions Of this part of ISO 4412. At the time of publication. the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO 4412 are encouraged to Investigate the possibility of applying the most recent editions of the standards indicated below.
3.3 anecholc room: Test room having boundaries which absorb essentially all of the incident sound energy over the frequency range of Interest, thereby affording free-field conditions over the measurement surface.
3.4 mean-square sound pressure: The sound pressure averaged in space and time on a mean- square basis.
NOTE 2 In practice, this is estimated by space and time averaging over a finite path length or over a number of fixed microphone positions.
3.5 mean sound pressure level (I): Ten times the logarithm to the base 10 of the ratio of the mean- square sound pressure to the square of the reference sound pressure, in decibels (dB).
NOTE 3 The weighting network or the width of the frequency band used should always be Indicated; for example, A-weighted sound pressure level, octave band sound pressure level. The reference sound pressure is 20 1Pa’.
3.6 sound power level L: Ten times the logarithm to the base 10 of the ratio of a given sound power to the reference sound power, in decibels (dB).
NOTE 4 The weighting network or the width of the frequency band used should always be indicated The reference sound power Is 1 pW’).
3.7 volume of source under test: Volume of the envelope of the who?e pump under test.
3.8 reference box: Hypothetical reference surface which is the smallest rectangular parallelepiped that just encloses the pump and any large directly- attached appendages (such as valve bodies or control handwheels) and which terminates on the reflecting planes.ISO 4412-3 pdf download.