This standard specifies the engineering method for determination of sound power level for noise on the reflecting plane in free sound field and the engineering method for determination of sound power level for noise in reverberation room. A movable microphone in reference sound source comparison method is adopted for the determination of sound power level for noise in reverberation room, and the multi-point test method is shown in Annex A.
This standard is applicable to the determination of sound power level for noise emitted by reciprocating pump unit including prime movers (hereinafter referred to as pump unit).
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments (excluding corrections), or revisions, of any of these publications do not apply to this standard. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition applies.
GB 3102.7 Quantities and units of acoustics (GB 3102.7-1993, eqv ISO 31-7:1992)
GB/T 3241 Octave-band and fractional-octave-band filters
GB/T 3767 Acoustics - Determination of sound power levels of noise sources using sound pressure - Engineering method in an essentially free field over a reflecting plane (GB/T 3767-1996, eqv ISO 3744:1994)
GB 3785 Electric, sonic properties and measuring methods for sound level meters
GB/T 3947 Acoustical terminology
GB/T 6881.2 Acoustics - Determination of sound power levels of noise sources - Engineering methods for small, movable sources in reverberant field - Part 1: Comparison method for hard-walled test rooms (GB/T 6881.2-2002, ISO 3743-1:1994, IDT)
GB/T 6881.3 Acoustics - Determination of sound power levels of noise sources-using sound pressure - Engineering methods for small movable sources in reverberant field - Part 2: Methods for special reverberation test rooms (GB/T 6881.3-2002, ISO 3743-2:1994, IDT)
JJG 176 Sound calibrators
JJG 188 Sound level meters
JJG 277 Reference sound sources
IEC 61183 Electroacoustics - Random-incidence and diffuse-field calibration of sound level meters
3 Terms and definitions
For the purposes of this standard, the terms and definitions given in GB/T 3947 and GB 3102.7 apply.
4 Determined quantity and measuring error
4.1 Determined quantity
A-weighted sound power level and seven octave sound power levels with a center frequency of 125~8,000Hz.
4.2 Measuring error
The standard deviation of A-weighted sound power level is not greater than 2dB and that of octave sound power level is not greater than the value specified in Table 1 according to the measurement based on this standard.
