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Pump noise measurement and evaluation methods (national standards)
GB 10890-89
Methods for Measuring and Evaluating Pump Noise
This standard provides a method for determining the sound power level of pumps, aligned with the international standard ISO 3746-1979, "Acoustics – Noise source sound power level measurement – Survey method." It outlines procedures for accurately measuring and evaluating pump noise, ensuring consistency and reliability in acoustic assessments.
The standard applies to submersible pumps, reciprocating pumps, and other types of pumps excluding those equipped with speed hydraulic couplings. When applicable, the sound power level method should be prioritized over the sound pressure level method. In case of disputes, the sound power level shall take precedence.
References include standards such as GB 3102.7 (Acoustics and Units), GB 3240 (Commonly used frequencies in acoustic measurements), GB 3241 (Sound and vibration analysis with 1/1 and 1/3 octave bands), GB 3768 (Simplified method for sound power level measurement), and others related to sound level meters, calibration, and acoustic terminology.
The sound power level measurement method described in this standard is consistent with GB 3768, allowing for more accurate assessment of pump noise. When precise determination is required, the influence of the prime mover’s noise (e.g., motor or internal combustion engine) must be considered. Measures like sound insulation covers may be necessary to minimize interference.
Measurement errors are defined as cumulative standard deviations caused by various factors. The acceptable error range for the pump sound source is not more than 4 dB, while for the same standard pump under identical conditions, it is not more than 3 dB.
The ideal acoustic environment for measurement includes a reflective surface (like the ground) without other reflective objects, creating a near-free field. Suitable environments include open areas or laboratories meeting specific acoustic requirements. For evaluation, the ratio A/S (sound absorption area over the measuring surface area) should be ≥1, or the environmental correction value K2 ≤7.
Background noise at each measuring point must differ from the pump noise by at least 3 dB. Wind speed during outdoor measurements should be below 6 m/s, and protective hoods should be used for cooling vents.
Test equipment, including sound level meters of type 2 or higher, must be calibrated before and after each measurement using a calibrator with ±0.5 dB accuracy. Regular verification according to JJG 188 ensures measurement reliability.
Pump installation and operating conditions require attention to outlet throttling, noise reduction from piping, and minimizing interference from other equipment. Operating speeds and pressures must adhere to specified tolerances based on pump type.
For sound pressure level measurements, microphones are placed on hemispherical or rectangular parallelepiped surfaces. Hemispherical surfaces are preferred, especially for single-stage or multi-stage pumps. Coordinates for measuring points are defined in Table 1, with specific height and distance requirements to avoid ground reflection errors.
Rectangular surfaces are used for large pumps, with measuring points placed at distances of 1m or more from the reference body. Multiple measuring points are required depending on the size and complexity of the sound source.
Background noise correction is applied when the difference between the measured sound level and background noise is less than 10 dB. Correction values are provided in Table 2, adjusting the measured levels accordingly.
The average sound pressure level on the measurement surface is calculated, followed by the determination of the A-weighted sound power level using the formula:
LWA = (LPA - K2) + 10 log(S / S0),
where LWA is the sound power level, S is the measurement surface area, and K2 is the environmental correction value.
Environmental correction value K2 can be determined either through standard sound source testing or by calculating sound absorption A using reverberation time T.
For sound pressure level measurements, the method involves placing microphones at specified positions around the pump, with adjustments made for background noise and distance attenuation. Frequency band measurements use 1/1 or 1/3 octave filters, with corrections applied if background noise is too close in level.
Noise evaluation uses a hemispherical surface for sound power level-based assessments. The sound pressure level on the evaluation surface is calculated using the formula:
LPA = LwA - 20 log(R / Ro) - 8.0,
where R is the radius of the evaluation surface, and Ro is the base radius.
Pump noise limits are divided into four levels (A, B, C, D) based on the pump's power. Formulas are provided to determine the noise limits LA, LB, and LC using the pump’s rated power.
This standard ensures that pump noise measurements are conducted systematically, reliably, and in accordance with international best practices.