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GB/T 2888-2008 English PDF (GBT2888-2008)

GB/T 2888-2008 English PDF (GBT2888-2008)

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GB/T 2888-2008: Methods of noise measurement for fans blowers compressors and roots blowers

This Standard specifies the noise measuring methods of the A-sound-level and sound pressure level. And it also specifies the noise measuring methods of the sound power level. This Standard applies to noise measurement for fans, turbo-blowers, turbo-compressors and Roots blowers.
GB/T ??2888?€?2008
GB
ICS 23.120
J 72
National Standard
of the PEOPLE Republic of China
Replacing GB/T 2888-1991
Methods of noise measurement for fans blowers
compressors and Roots blowers
ISSUED ON. JULY 9, 2008
IMPLEMENTED ON. FEBRUARY 1, 2009
Issued by. State Administration for Quality Supervision, Inspection and Quarantine of the People's Republic of China;
Standardization Administration of China.
Table of Contents
Foreword??...??3
1 Scope??...??5
2 Normative??references??...??5
3 Terms,??symbols??and??units??...??5
4 Measurement??items??...??8
5 Measurement??condition??...??8
6 Measuring??instruments,??equipment,??rack??and??its??requirements??...??9
7 Measuring??device??...??9
8 Measuring??procedure??...??10
9 Measuring??method??...??10
10 Processing??of??measurement??data??...??20
11 Measurement??reports??...??22
Annex??A??...??24
Annex??B??...??33
Foreword
This Standard is the revision to GB/T 2888-1991 Methods of noise measurement for fans blowers compressors and Roots blowers.
Compared with GB/T 2888-1991, the changes of the main technical contents of this Standard are as follows.
?€? Revise the title ?€?Main Content and Scope of Application?€? to ?€?Scope?€?.
?€? Reconfirm the validity of the reference standards, and add corresponding standards. ?€? Revise the title ?€?Code?€? to ?€?Unit?€? in Chapter 3.
?€? Increase the fans sound source of free inlet and free outlet in 3.2, and combine the notes of icons and figures.
?€? The statement ?€?When carrying out outlet aerodynamic performance test of fans?€? specified in 9.2.1.1 is revised as ?€?When carrying out performance test of free inlet and pipeline outlet of fans?€?, and icons for description are added.
?€? The statement ?€?When carrying out inlet aerodynamic performance test of fans?€? specified in 9.2.1.2 is revised as ?€?When carrying out performance test of pipeline inlet and free outlet of fans?€?, and icons for description are added.
?€? The statement ?€?When carrying out inlet and outlet aerodynamic performance test of fans?€? specified in 9.2.1.3 is revised as ?€?When carrying out performance test of pipeline inlet and pipeline outlet of fans?€?, and icons for description are added. The statement ?€?Measure the air outlet radiation noise from the vent duct. The measuring position D is at the 45?? direction from the air outlet axis. The distance from the outlet center is the standard length. The measurement position shall be selected at the area without airflow vortex?€?.
?€? Add icons?€? noted in 9.2.1.4, 9.2.1.5 and 9.2.2.
?€? In 10.2.1, when the test speed n is different from rated speed n0, the sound pressure level conversion formula is modified.
?€? In 10.2.2, when the atmospheric pressure and the temperature are significantly different with that in the standard state, the sound pressure level conversion formula is modified.
?€? Add A-sound-level calculation formula of fans noise in 10.2.3.
?€? Units and icons?€? notes of some parameters in the previous standard are modified. Annex A and Annex B of this Standard are informative.
This Standard was proposed by China Machinery Industry Federation.
This Standard shall be under the jurisdiction of National Technical Committee on Fans of Standardization Administration of China
Drafting organizations of this Standard. Shenyang Blower (Group) Co., Ltd., Beijing Shiji Jingye Noise Vibration Control Technology Co., Ltd., and Changsha Blower Co., Ltd. Main drafters of this Standard. Chen Zhongcai, Shao Bin, Zhu Guixiu, Jiang Yunzhu, Xiao Binshi, and Wang Dongguo.
The previous standard replaced by this Standard are as follows.
?€? GB 2888-1982, GB/T 2888-1991.
Methods of noise measurement for fans blowers compressors
and Roots blowers
1 Scope
This Standard specifies the noise measuring methods of the A-sound-level and sound pressure level. And it also specifies the noise measuring methods of the sound power level. This Standard applies to noise measurement for fans, turbo-blowers, turbo-compressors (hereinafter referred to as fans) and Roots blowers.
2 Normative references
The articles contained in the following documents have become part of this Standard when they are quoted herein. For the dated documents so quoted, all the modifications (excluding corrections) or revisions made thereafter shall not be applicable to this Standard. For the undated documents so quoted, the latest editions shall be applicable to this Standard.
GB/T 1236 Industrial fans-Performance testing using standardized airways GB/T 3947 Acoustical terminology
GB/T 10178 Industrial fans-performance testing in situ (GB/T 10178-2006, ISO 5802. 1997, IDT)
JB/T 3165 Thermodynamic performance test for centrifugal and axial blowers and compressor
JB/T 8690 Industrial fans noise limited value
JB/T 8941.2 Roots type blowers for general purpose - Part 2. Performance test methods 3 Terms, symbols and units
3.1 A-sound-level
With A-sound-level meter or other measuring instrument that is equivalent, the noise level measured by A-weighting network is called A-sound-level, expressed as LA. The unit is Decibel, with unit symbol of dB. In order to make it clear, this Standard uses dB(A) to express A-characteristic weighting.
3.2 Sound source
The sound sources generated by enclosure, inlet, outlet and other sources of the fans and Roots blowers. The specific positions of the sound sources (indicated by X) are shown in Figure 1-7.
Figure 1 Sound source of fans?€? free inlet and free outlet
Figure 2 Sound sources of fans?€? free inlet and pipeline outlet
Figure 3 Sound sources of fans?€? pipeline inlet and free outlet
Figure 4 Sound sources of fans?€? pipeline inlet and pipeline outlet
Figure 5 Sound sources of turbo-blowers and turbo-compressor
Figure 6 The Roots blowers?€? sound source that with the inlet duct and outlet duct are in the same line
Figure 7 The Roots blowers?€? sound source that the inlet duct and the outlet duct is mutually perpendicular
3.3 Standard sound source
Standard sound source is the sound source that has very stable output and good omni- direction within the range of the measurement frequency, and it is calibrated in anechoic chamber or reverberation chamber.
3.4 Standard length
The distance from noise measuring point to sound source point. When measuring the noise at inlet and outlet of the fans, and If the diameter of impeller is less than or equal to 1 m, the standard distance is 1m; if the diameter of impeller is greater than 1m, the standard length is equal to impeller diameter. Standard length is expressed as L. When measuring the noise of fans and Roots blowers?€? enclosure, it shall take the standard length as 1 m.
3.5 Measured value
The read value of the sound level meter after the background noise is corrected. 3.6 Assumed sound source surface
Taking sound source into account, the minimum assumed cuboid surface of basal plane with good sound insulation. The protuberances of fans and Roots blowers are deemed as the main parts of sound sources.
3.7 Semi-free field
The sound field in which sound source can be set, and which has a reflecting surface. 4 Measurement items
Under the operating conditions specified, measure A-sound-level and the frequency-band sound pressure level of fans and Roots blowers.
5 Measurement condition
5.1 Measurement environment
5.1.1 Measurement site
For measurement sites, the sites without reflection conditions (the ground is excluded) shall be selected as possible. In addition, the fans or Roots blowers to be measured shall be in operating condition. When the distance from the measuring point to the sound source point is 1 time and 2 times of the standard length, the difference value of A-sound-level shall not be less than 5 dB(A).
If above conditions can not be met, the measuring field conditions (the indoor size, device size, configuration, sound field measurement results) shall be recorded. 5.1.2 Background noise
Measuring site shall avoid the influence of background noise. The background A-sound- level and frequency-band sound pressure level shall be at least 10 dB lower than that of the machine being tested. When the difference value is 4dB ?€? 9dB, it shall be corrected according to Table 1. When it is less than 3 dB, noise measurement shall not be conducted. Table 1
The difference of the measured value with or
without measuring objects/dB
4, 5 6, 7, 8, 9
Corrected value/dB -2 -1
5.2 Operating conditions
In general, noise shall be measured under the condition of rated speed and rated flow. It can also be measured under other conditions as agreed b...

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