This specification is applicable to the measurement of the sound absorption coefficient of sound-absorbing materials and the sound absorption of individual objects in a reverberation room. GBJ 47-1983 Reverberation Room Method Sound Absorption Coefficient Measurement Specification GBJ47-1983 Standard Download Decompression Password: www.bzxz.net

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National Standard of the People's Republic of China
Specification for the measurement of sound absorption coefficient by reverberation chamber method
GBJ47—83
(Trial)
1983Beijing
Engineering Construction Standard Full-text Information System
W Engineering Construction Standard Full-text Information System
National Standard of the People's Republic of China
Specification for the measurement of sound absorption coefficient by reverberation chamber method
GBJ47—83
(Trial)
Editor Department: Ministry of Radio and Television of the People's Republic of ChinaApproval Department: People's Republic of China State Economic Commission of the Republic of China Trial date: June 1, 1983
Engineering Construction Standards Full Text Information System
Engineering Construction Standards Full Text Information System
Notice on Issuing the "Measurement Specification of Sound Absorption Coefficient by Reverberation Chamber Method"
Jingji (83) No. 04
According to the requirements of the former State Construction Commission (81) Jianfa Shezi No. 546 Notice, the "Measurement Specification of Sound Absorption Coefficient by Reverberation Chamber Method" compiled by the National Acoustic Standardization Technical Committee and jointly compiled by the Ministry of Radio, Film and Television and relevant units has been reviewed by the plenary meeting of the National Acoustic Standardization Technical Committee. The "Measurement Specification of Sound Absorption Coefficient by Reverberation Chamber Method" GBJ47-83 is now approved as a national standard and will be implemented on a trial basis from June 1, 1983. This specification is managed by the Ministry of Radio, Film and Television, and its specific interpretation and other work are the responsibility of the Design Institute of the Ministry of Radio, Film and Television.
National Economic Commission
January 5, 1983
Engineering Construction Standards Full Text Information System
Engineering Construction Standards Full Text Information System
Preparation Instructions
This specification is jointly prepared by our department, the Institute of Acoustics of the Chinese Academy of Sciences, the China Academy of Building Research, Tsinghua University, Nanjing University and Tongji University. During the preparation process, through investigation and research, we systematically summarized the experience of sound absorption coefficient measurement by the reverberation chamber method in my country, conducted certain experimental research, and referred to the relevant materials of the International Organization for Standardization. We widely solicited opinions from relevant units across the country, and finally the draft was reviewed and finalized by the plenary meeting of the National Acoustics Standardization Technical Committee. During the trial implementation of this specification, we hope that all units will pay attention to accumulating information and summarizing experience. If you find that there is a need for modification and supplementation, please send your opinions and relevant information to our design institute. Ministry of Radio and Television
December 1982wwW.bzxz.Net
Engineering Construction Standards Full Text Information System
Engineering Construction Standards Full Text Information System
Chapter 1
Chapter 2
Measurement Equipment
Section 1 Reverberation Chamber
Section 2
Sound Source Equipment
Section 3
Receiving Equipment.
Section 4
Tested Items
Chapter 3 Measurement Methods
Section 1 Measurement of Reverberation Time
Section 2
Calculation of Sound Absorption Coefficient and Sound Absorption Quantity·
Result Table
Chapter 4
Appendix 1
Appendix 2
Appendix 3
Appendix 4
Glossary
Determination of the number of suspended diffusers
Definition and calculation method of repeatability
Explanation of terms used in this specification
Engineering Construction Standard Full-text Information System
Engineering Construction Standard Full-text Information System
Chapter 1 General Provisions
Article 1.0.1 This specification is formulated to unify the measurement methods and measurement conditions of various laboratories and make the sound absorption coefficients of the same structure (or object) measured by various laboratories as close as possible.
Article 1.0.2 This specification is applicable to the measurement of the sound absorption coefficient of sound-absorbing materials and the sound absorption of a single object in a reverberation room.
Engineering Construction Standard Full Text Information System
Engineering Construction Standard Full Text Information System
Chapter 2
Measurement Device
Section 1 Reverberation Room
Article 2.1.1 The volume of the reverberation room should be greater than 200 cubic meters. Note: For existing reverberation rooms with a volume less than 200 cubic meters, the lower limit frequency should be determined as follows: f=125|2001/3
f—lower limit frequency of the reverberation room (Hz)
—volume of the reverberation room (m3).
Article 2.1.2 The shape of the reverberation room can be rectangular or other shapes composed of non-parallel and irregular interfaces. No two of the dimensions of the room should be equal, nor should they be in an integer ratio.
The maximum linear dimension (1max) in the room should not be greater than 1.9V1/3 (for a rectangular room, the maximum linear dimension is the main diagonal).
Article 2.1.3 Effective diffusion measures should be taken in the reverberation room to achieve sufficient diffusion of its decaying sound field. Regardless of the shape of the room, it is advisable to use hanging or fixed wall diffusers or rotating diffusers. The number and specifications of hanging diffusers can be determined according to Appendix 2. When using rotating diffusers or fixed diffusers, the same effect as hanging diffusers should be achieved. Article 2.1.4 For a reverberation room with a volume of 200 cubic meters, when no test specimens are loaded, the sound absorption of each frequency band should be less than the value in Table 2.1.4. Sound absorption of each frequency band
Frequency (Hz)
Sound absorption (m2)
Frequency (Hz)
Sound absorption (m2)
Note: If the volume of the reverberation room is greater than 200 cubic meters, the sound absorption in the table should be multiplied by (V/200)2/3. Engineering Construction Standard Full Text Information System
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Article 2.1.5 The frequency characteristics of the sound absorption of the reverberation room should be a smooth curve without obvious peaks or valleys (that is, the difference between the sound absorption of any 1/3 octave and the average sound absorption of the two adjacent 1/3 octaves should not be greater than 15%). Section 2 Sound Source Equipment
Article 2.2.1 The loudspeaker or loudspeaker group used for sound in the reverberation room should be as non-directional as possible. When measuring each frequency band below 300 Hz, the position of the loudspeaker should be changed once. The distance between the two positions should be greater than 3 meters. It is also possible to use two equivalent and separated sound sources or two independent sound source systems to rotate the sound.
Article 2.2.2 The width of the noise of the sound source signal band should be 1/3 octave. Broadband noise and computer-controlled real-time analyzers can be used to measure each frequency band of the full frequency band at the same time. When the room is empty, the average sound pressure level spectrum of the indoor sound source should be roughly pink noise or white noise, and the difference in sound pressure level between two adjacent 1/3 octave bands should be less than 6 dB. Article 2.2.3 The difference between the sound level of the steady-state sound source signal and the background noise level before decay should not be less than 40 dB.
The duration of the steady-state signal before cutting off the sound source should not be shorter than the reverberation time of the frequency band. Section 3 Receiving Equipment
Article 2.3.1 The receiving equipment should include microphones, amplifiers, filters and recording equipment. The microphone should be as non-directional as possible. The measurement bandwidth should be 1/3 octave.
The recording equipment should be suitable for recording a decay rate of at least 300 dB/s. Section 4 Test Pieces
Article 2.4.1 The plane test piece should be a whole. The test piece area should be 10 to 12 square meters. If the volume of the reverberation chamber is less than 200 cubic meters or greater than 250 cubic meters, the area of ​​the specimen can be changed by multiples of (V/200)2/3.
Article 2.4.2 When the shape of the plane specimen is rectangular, its length-to-width ratio should be 0.6-1.0. Article 2.4.3 The edge of the plane specimen should be closed with a reflective frame. The frame should be tightly attached to an interface in the room. The distance between the frame and any other interface should not be less than 1 meter. The thickness of the frame should not be greater than 20 mm.
When measuring a structure with a large cavity behind the specimen (such as a ceiling), its side should be closed with a reflective surface and should be perpendicular to the specimen surface. Article 2.4.4 The single object to be measured (such as a person, a seat, a space sound absorber, etc.) should be arranged according to the conditions of use. People or seats should be placed on the ground, but the distance from any other interface and microphone should be greater than 1 meter; spatial sound absorbers should also be treated according to the same principle. Article 2.4.5 When a single object is used as a test piece, the change in the measured sound absorption should be 1 to 12 square meters.
Article 2.4.6
The edges of the single object being measured (single or combined) should be treated according to the conditions of use. If people and seats are measured, they should be closed with reflective materials and the height should be 1 meter.
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Chapter 3 Measurement Methods
Section 1 Measurement of Reverberation Time
Article 3.1.1. The measurement of reverberation time shall be carried out on the 1/3 octave sequence of the following center frequencies:
Note: If necessary, a receiving filter with a 1/3 octave bandwidth may also be used, but only the following 1/1 octave sequence shall be measured: 125
3.1.2. The measurement of reverberation time shall have at least three microphone measuring points, and the distance between each measuring point shall be greater than 1/2 of the wavelength (>) of the lowest center frequency of the measured frequency band. Each microphone measuring point shall be far away from the sound source, the test piece and the boundary surface (including the diffuser), and the minimum values ​​of these distances shall be: 2 meters, 1 meter, and 1 meter respectively. 3.1.3. The decay curve used to calculate the reverberation time shall be linear within the range of 5 to 25 dB below the steady-state sound level. The reverberation time shall be the average slope of the line segment. The bottom of the line segment shall be at least 15 dB higher than the background noise, and care shall be taken not to excessively extend the 20 dB linear range to the non-linear part. Article 3.1.4 When the broken line decay curve is processed according to the linear decay curve, the following conditions shall be met: each section shall not be less than 10 decibels, and the difference in the slope measured after each section is extended shall not be greater than 10%.
Decay curves that do not meet the requirements shall be excluded from the calculation. Article 3.1.5 The reverberation time of each 1/3 octave shall be the arithmetic mean of the results obtained from each excitation at each microphone or speaker position. The reverberation time of the empty room (T60-1) and the reverberation time after the material is placed (T60-2) shall be calculated to two decimal places.
The number of decay curves measured for each 1/3 octave shall not be less than the provisions of Table 3.1.5, and the decay curve shall meet the requirements of Articles 3.1.3 and 3.1.4 of this specification. Allowable value of decay curve number
Measurement frequency (Hz)
100~250
315~800
1000~5000
Number of decay curves (lines)
Decay of each microphone or field sounder point
Number of curves (lines)
If the sound absorption coefficient of the tested piece in the low frequency band is large, the number of curves to be measured should be appropriately increased. The average value can also be read automatically by overlapping the number of curves that meet the above requirements. Article 3.1.6 During the measurement of the reverberation time of the empty room and the reverberation time of the material placed in it, the changes in the temperature and relative humidity in the room should meet the requirements of Table 3.1.6. Difference in temperature and humidity changes during measurement
Relative humidity
40~60%
Above 60%
Relative humidity difference
Temperature difference
Section 2 Calculation of sound absorption coefficient and sound absorption Table 3.1.6
Minimum temperature
Article 3.2.1 The sound absorption coefficient and sound absorption shall be calculated according to the following formula based on the reverberation time of each frequency band:
In the formula, α%—
C·nT60-2
Sound absorption coefficient of reverberation room method, %=
(3.2.1 —1)
(3.2.1—2)
To avoid confusion with the sound absorption coefficient of a plane wave at a specific incident angle, the subscript s must be added. α may be greater than 1, so it is not expressed as a percentage.
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A1——Sound absorption of the empty reverberation chamber (m); A2—Sound absorption of the reverberation chamber after the specimen is placed (m); A——Sound absorption of a single object (m); s——Speed ​​specimen area (m2);
n——Number of specimen units;
T60-1——Reverberation time before the specimen is placed (seconds); T60-2——Reverberation time after the specimen is placed (seconds); C——Sound speed in air (m/s),
C=331.5+0.5t, (t: air temperature °C). Article 3.2.2 When the volume of the specimen is greater than 1/100 of the volume of the reverberation chamber, the volume of the reverberation chamber in formula 3.2.1 should be corrected. Engineering Construction Standards Full Text Information System
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