ISO 4412-3:1991 pdf download – Hydraulic fluid power – Test code for determination of airborne noise levels
From these Sound power levels, if required, refer- ence Sound pressure levels may be calculated for reporting purposes (see clause 1 1 ). For general purposes, the frequency range of inter- est includes the one-third octave bands with centre frequencies between 1 00 Hz and 1 0000 Hz.‘) This patt of ISO 441 2 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 441 2. At the time of publication, the editions indicated were valid. All Standards are subject to revision, and Parties to agreements based on this patt of ISO 441 2 are encouraged to investi- gate the possibility of applying the most recent edi- tions of the Standards indicated below.
3.3 anechoic 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 CL..): Ten times the logarithm to the base 1 0 of the ratio of the mean- Square Sound pressure to the Square of the refer- ence Sound pressure, in decibels (dB). NOTE 3 The weighting network or the width of the fre- quency band used should always be indicated; for exam- ple, A-weighted Sound pressure level, octave band Sound pressure level. The reference Sound pressure is 20 IIPaz).
3.6 Sound power level L,: Ten times the logarithm to the base IO of the ratio of a given Sound power to the reference Sound power, in decibels (dB).
4 Measurement uncertainty
With the exception of the measurement environment specified in clause 5, use methods of measurement which tend to result in Standard deviations which are equal to or less than those given in table 1 . To meet this requirement, use the engineering methods given in ISO 3744: 1 981 , clause 4 and annex A.
The Standard deviations given in table 1 include the effects of allowable variations in the positioning of the measurement Points and in the selection of any prescribed measurement surface, but exclude vari- ations in the Sound power output of the Source from test to test. NOTE 5 The A-weighted Sound power level will in most practical cases be determined with a Standard deviation of approximately 2 dB.
5 Test environment
Tests shall be conducted in an environment gener- ally in accordance with that described in ISO 3744 and which provides free-field conditions over two mutually perpendicular reflecting planes, both of which extend beyond the projected area of the microphone measuring array. CaYibrate the acoustic test environment thus formed and ascertain the environmental corrections for each frequency band of interest, using the pro- cedures described in ISO 3744:1 981 , annex A.