This standard specifies the noise measurement methods for A-level and sound pressure level, and also specifies the noise measurement methods for sound power level. This standard is applicable to the noise measurement of general types of fans, turbo blowers, turbo compressors and Roots blowers. GB/T 2888-1991 Noise measurement methods for fans and Roots blowers GB/T2888-1991 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Methods of noise measurement for fans, blowers compressors and Roots blowersSubject content and scope of applicationbZxz.net
GB/T 2888-91
Replaces GB 2888-·82
This standard specifies the noise measurement methods of A sound level and sound pressure level, and also specifies the noise measurement methods of sound power level. This standard is applicable to the noise measurement of general types of fans, turbo blowers, turbo compressors (hereinafter referred to as fans) and Roots blowers.
2 Reference standards
GB1236 Test method for aerodynamic performance of ventilator GB3947 Terminology of acoustic terms
GB10178 Field test of ventilator
JB3165 Thermal performance test of centrifugal and axial flow blower compressors ZBJ72031
General purpose Roots blower performance test method 3 Terms, symbols, codes
3.1A sound level
The noise level indicated by the A-weighting network using a sound level meter or an equivalent measuring instrument is called the A sound level, expressed in L. The unit is decibel, and the unit symbol is dB. This standard is clearly expressed in dB(A) with A characteristic weighting. 3.2 Sound source
The noise source generated by the fan and Roots blower casing, air inlet, air outlet, etc., the specific sound source locations are as follows: a. Air inlet of a ventilator that opens to the atmosphere without an external duct (Figure 1); Figure 1
Note: Standard sound source.
Approved by the State Administration of Technical Supervision on November 6, 1991 and implemented on August 1, 1992
GB/T2888-91
Air outlet of a ventilator that opens to the atmosphere without an external duct (Figure 2); Figure 2
Casing of a ventilator with both the air inlet and the air outlet connected to ducts (Figure 3); Figure 3
d. Casing of a turbine blower and turbine compressor (Figure 4); Figure 4
Casing of a Roots blower (Figure 5, Figure 6).
3.3 Standard sound source
GB/T2888-91
A sound source that has very stable output within the measurement frequency range, good omnidirectionality and has been calibrated in an anechoic chamber or reverberation chamber is the standard sound source.
3.4 ​​Standard length
The distance from the noise measurement point to the sound source point. When measuring the noise at the inlet and outlet of the fan, when the impeller diameter is less than or equal to 1m, the standard length is 1m. When the impeller diameter is greater than 1m, the standard length is equal to the impeller diameter. The standard length is represented by L. When measuring the noise of the fan and Roots blower casing, the standard length is 1m. 3.5 Measurement value
The value after the background noise correction is made to the reading of the sound level meter. 3.6 Assumed sound source surface
The minimum assumed rectangular surface ending at the ground, including the sound source. The main body of the fan and Roots blower is regarded as a protrusion of the sound source and is included in it.
3.7 Semi-free field
A sound source can be set up, and there is a sound field with a reflecting surface. 4 Measurement items
Measure the A sound level and band sound pressure level around the fan and Roots blower under the specified operating conditions. 5 Measurement conditions
5.1 Measurement environment
5.1.1 Measurement location
GB/T2888--91
The measurement location should be a location with no reflection conditions except the ground, and the fan and Roots blower to be measured should be in operation. When the distance between the measurement point and the sound source is 1 and 2 times the standard length, the difference in the A sound level should not be less than 5dB(A). If the above conditions cannot be met, the measurement location status (indoor dimensions, device dimensions, configuration, sound field measurement results) should be recorded. 5.1.2 Background noise
The measurement location should avoid the influence of background noise. The background A sound level and octave band sound pressure level should be at least 10dB lower than the measured machine. When the difference between the two is 4~~~9 dB, it should be corrected according to Table 1. Table 1
Difference in measured values ​​with and without the measured object, dB correction value, dB
5.2 Operating conditions
6;7;8,9
Noise measurement should generally be carried out under rated speed and flow conditions. When agreed with the user, it can also be measured under other conditions, but the specific operating conditions should be clearly recorded.
The setting of rated speed and flow is allowed to be within ±5% of the rated value. 6 Measuring instruments, equipment, benches and their requirements The measuring instruments are sound level meters and octave band filters or equivalent measuring instruments. Sound level meters and octave band filters should comply with relevant standards.
7 Measuring devices
The measuring devices of fans and Roots blowers should comply with the corresponding performance test method standards. The following requirements should be met during installation: Minimize the noise generated by the vibration of the measured fan and Roots blower and the reflected sound from the ground and other objects; a.
The motor noise is regarded as background noise (except when the motor and fan, Roots blower cannot be separated); h
When measuring the noise of the fan and Roots blower casing, the noise of the pipeline inlet and outlet is regarded as background noise, and silencer treatment should be performed if necessary; when measuring the noise of the fan inlet and outlet, the noise at the far end of the wind tube is regarded as background noise, and silencer treatment should be performed if necessary. d.
8 Measurement procedure
When measuring the noise of the fan and Roots blower, it is generally carried out at the same time as the aerodynamic performance test. The noise measurement value of each operating point should be measured at the same time as the corresponding aerodynamic performance measurement value. If the field test is performed, it can be measured under the operating condition. 9 Measurement method
9. 1 Measurement steps
9.1.1 The weighting network of the sound level meter uses the A file. 9.1.2 First, measure the background noise and sound field attenuation law of the measuring point. 9.1.3 The microphone of the sound level meter should point to the sound source, and the measurer should face the side of the sound source. 9.1.4 The minimum reading of the sound level meter is 0.5dB. When the indication value changes, take the average value of the pointer swing. However, when the indication value changes by more than ±4dB, the measurement should be stopped.
9.1.5 The sound level meter needs to be calibrated before and after measurement. When the error exceeds the accuracy of the sound level meter, it should be measured again. 9.2 Measurement point position
9.2.1 Measurement point position of ventilator
GB/T2888—91
9.2.7.1 When the ventilator is tested for aerodynamic performance, the noise radiated from the air inlet is measured. The measurement point position S (see Figures 7 to 13) is on the axis of the air inlet, and the distance from the air inlet is the standard length. so
GB/T2888—91
9.2.1.2 When the fan is tested for air intake and air flow performance, the noise radiated from the air outlet is measured. The measuring point position D (see Figures 14 to 17) is at 45° to the air outlet axis, and the distance from the air outlet is the standard length. The measuring point position should be selected in the area without air flow vortex and the place where the motor noise has less influence.
GB/T2888—91
9.2.1.3 When the fan is tested for air intake and air outlet performance, the noise radiated from the air inlet of the air intake duct is measured. The measuring point position S (see Figures 7 to 13) is on the air inlet axis of the air intake cylinder, and the distance from the air intake of the air intake cylinder is the standard length. 9.2.1.4 When the air inlet and outlet of the fan are connected to the pipeline, the noise radiated by the casing is measured. The measuring point is located in the horizontal plane of the fan main shaft, on the straight line passing through the geometric center of the impeller, 1m away from the casing. The measuring point positions C1.C2, M1, M2., see Figures 18 to 28. The measured values ​​of the measuring points M1 and M2 on the motor side are generally used as reference. However, the motor directly connected to the fan impeller is part of the fan sound source.
GB/T 2888--91
GB/T 2888-
GB/T 2888-—91
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GB/T 2888—-91
Figure 28
9.2.1.5 When both the air inlet and the air outlet are open to the atmosphere, the position of the measuring point shall be determined in accordance with 9.2.1.1, 9.2.1.2 and Figures 29 to 31. Figure 29
GB/T 2888—91
9.2.2 Position of measuring points for Roots blowers, turbine blowers and compressors 1moMl
a. For Roots blowers, turbine blowers and turbine compressors, the measurement is generally carried out at a distance of 1m from the surface in three directions around, and the measuring point is in the horizontal plane of the machine main shaft. The measuring point positions of Roots blowers are shown in Figures 32 to 33, the measuring point positions of turbine blowers are shown in Figures 34 to 37, and the measuring point positions of turbine compressors are shown in Figures 38 to 41;
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