GBJ 76-1984 Specification for measurement of reverberation time of halls
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Engineering Construction Standard Full-text Information System
National Standard of the People's Republic of China
Measurement Specification of Hall Reverberation Time
GBJ76-84
1985 Beijing
Engineering Construction Standard Full-text Information System
W Engineering Construction Standard Full-text Information System
National Standard of the People's Republic of China
Measurement Specification of Hall Reverberation Time
Editor: Qing
Approval Department: State Planning Commission of the People's Republic of China Implementation Date: 1 June 1, 1985
Engineering Construction Standards Full Text Information System
Engineering Construction Standards Full Text Information System
Notice on the Release of the "Measurement Specification for Hall Reverberation Time"bzxZ.net
Ji Biao [1984] No. 2496
According to the requirements of the former State Construction Commission (81) Jianfa She Zi No. 546, the "Measurement Specification for Hall Reverberation Time" compiled by Tsinghua University, which is organized by the National Acoustic Standardization Technical Committee, has been reviewed by the National Acoustic Standardization Technical Committee. The "Measurement Specification for Hall Reverberation Time" GBJ76-84 is now approved as a national standard and will be implemented from June 1, 1985. Tsinghua University is responsible for the specific interpretation of this specification.
National Planning Commission
December 4, 1984
Engineering Construction Standards Full Text Information System
Engineering Construction Standards Full Text Information System
Preparation Instructions
This specification is based on the requirements of the former National Capital Construction Commission (81) Jianfashezi No. 546. The National Acoustic Standardization Technical Committee is responsible for the centralized organization and is specifically compiled by Tsinghua University.
In the process of compiling this specification, we conducted extensive investigations, carefully summarized the years of practical experience and feasible measurement methods of relevant units engaged in architectural acoustics in China, conducted certain comparative tests on different types of halls, and referred to relevant materials such as ISO3382 "Acoustics-Measurement of Reverberation Time in Halls" of the International Organization for Standardization. The first draft of the specification was proposed, and the opinions of relevant units in China were widely solicited. Finally, it was reviewed and finalized by the National Acoustic Standardization Technical Committee. During the implementation of this specification, we hope that all units will pay attention to accumulating information and summarizing experience. If you find any need for modification or supplementation, please send your opinions and relevant information to our school for reference in future modifications.
Tsinghua University
November 12, 1983
Engineering Construction Standards Full Text Information System
Engineering Construction Standards Full Text Information System
Chapter 1 General
Chapter 2 Measurement System
Section 1 General Provisions
Section 2 Sound Source Equipment
Section 3 Receiving Equipment
Chapter 3 Measurement Methods
Section 1 Measurement Frequency
Section 2 Selection of Measurement Points
Section 3 Number of Records and Selected Values
Chapter 4 Result Expression
Section 1 Expression of Reverberation Time
Section 2 Contents of Measurement Report
Appendix—
Term Explanation
Appendix 2
Appendix 3
Reverberation Time Measurement Report·
Terms Used in This Code
Engineering Construction Standard Full-text Information System
Engineering Construction Standard Full-text Information System
Chapter 1 General Provisions
This code is formulated to unify the measurement system and measurement method of hall reverberation time. Article 1.0.1
This code is specially formulated to make the results of measurements of different units have a unified basis for mutual comparison. Article 1.0.2 This code is applicable to the measurement of reverberation time of general halls. Article 1.0.3 In addition to implementing this code, other relevant national standards or specifications in force should also be observed when measuring hall reverberation time. Engineering Construction Standard Full Text Information System
Engineering Construction Standard Full Text Information System
Chapter 2 Measurement System
Section 1 General Provisions
Article 2.1.1 The hall to be measured should provide three conditions to be measured, namely, full-field condition, rehearsal condition and empty field condition.
When measuring any of the above conditions, the doors and windows of the hall should be closed, and the door curtains should be unfolded.
Section 2 Sound Source Equipment
Article 2.2.1 The noise signal should be generated through a 1/1 octave or 1/3 octave filter as much as possible. The filter should meet the requirements of the current national standard "1/1 and 1/3 octave filters for sound and vibration analysis". The speaker system used for sound generation during measurement should be non-directional. The sound source for measurement (centralized sound source) should be placed at the center of the main curtain line, preferably 1.5 meters above the ground.
Article 2.2.2 In halls with long reverberation time (greater than 1.5 seconds below 1000 Hz), pulse signals (such as signal guns, firecrackers and balloons, etc.) can also be used as sound sources. At this time, it is necessary to ensure that the sound signal includes the width of all measured frequency bands. Within the measured frequency band, the sound pressure level shall meet the requirements of Article 2.2.4 of this specification. Article 2.2.3 When using symphony as the sound source, the frequency band range of the sound signal taken for measurement shall include the width of the measured frequency band and shall have a sufficiently long rest time that will not affect the decay.
Note: The musical instrument should be able to damp immediately when the music stops. The musical instrument that cannot be damped immediately should not be included in the sound source, especially the wind instrument. Article 2.2.4 At all measuring points, the sound pressure level of each measured frequency before decay shall be 35 decibels higher than the corresponding background noise level. Article 2.2.5 The same sound source should be used to measure the reverberation time of the same hall in full, empty or rehearsal conditions.
Section 3 Receiving Equipment
Article 2.3.1 The receiving system should include a microphone, a measuring amplifier, a 1/3 octave filter and a recording instrument. The equipment of the receiving system should meet the following requirements: 1. The microphone should be non-directional.
2. The recording system should use a sound level recorder (level recorder). When recording, the pen speed of the selected recorder should not affect the decay characteristics, and the paper speed of the recorder should be adjusted so that the slope of the decay curve is close to 45
The recording system can also use a recording instrument with equivalent performance to the sound level recorder (level recorder) that can directly read the reverberation time number. If a recorder (tape recorder) is used to record sound decay, the recording and playback system of the recorder (tape recorder) shall have linear frequency characteristics within the frequency range required by this specification, and its signal-to-noise ratio shall not be less than 40 decibels.
The recorder (tape recorder) used for measurement shall comply with the provisions of the current national standard "Basic Parameters and Technical Requirements for Tape Recorders" for reel-type second-level and cassette-type third-level. Engineering Construction Standard Full-text Information System
Engineering Construction Standard Full-text Information System
Chapter 3
Measurement Method
Section 1 Measurement Frequency
Article 3.1.1 The frequency selected for measuring reverberation time shall not be less than the following 6 octave center frequencies:
20004000 Hz
1252505001000
If necessary, the center frequency with a frequency interval of 1/3 octave shall be added. The selection of frequency shall comply with the current national standard "Common Frequencies in Acoustic Measurement".
Section 2 Selection of Measurement Points
Article 3.2.1 The number of measurement points for measuring the reverberation time of a hall should not be less than 3 when the hall is full and should not be less than 5 when the hall is empty. For asymmetric halls, the number of measurement points should be appropriately increased. The measurement points selected in Article 3.2.2 should be representative. For symmetrical halls, the measurement points must be selected on the longitudinal axis 1.5 meters away from the longitudinal centerline and in the side seats. The selection of measurement point locations should include about 1/3 of the front of the pit seats, under the platform and the side seats, but should avoid being in the direct sound field.
For halls with balconies, there should be measurement points in the balcony area. The measurement point positions when the hall is full should try to coincide with the measurement points when the hall is empty. If necessary, additional stage measurement points should be added. For halls with obvious coupling, measurement points should be added outside the coupling variation, and the results will not be included in the average of the entire hall. Article 3.2.3 The height of the measuring point from the ground should be 2.3 meters, and the distance from the wall should be greater than the half wavelength of the lower limit center frequency of the measured frequency band. Section 3 Number of records and selected values
Article 3.3.1 The effective reverberation time of each measuring point for each measured frequency should not be less than three decay curves.
Article 3.3.The decay range of the two decay curves should not be less than 35 dB. The decay curve within this range should be linear from 5 dB below the starting level to 25 dB, and the reverberation time should be determined by the slope of this straight line. When the decay curve is in the shape of a broken line, the front fold should be taken, that is, the linear part from 5 dB below the starting level to 15 dB, and the reverberation time should be determined from this. The reverberation time taken according to this provision should be stated in the report. When drawing the reverberation time frequency characteristic curve, this point should be represented by a hollow circle to distinguish it from other values. When all the curves measured at certain measuring points or at certain frequencies are non-linear curved curves, they should also be discussed and explained in the report, and the decay curve should be attached if necessary. The value obtained should not be included in the overall average. Engineering Construction Standard Full Text Information System
Engineering Construction Standard Full Text Information System
Chapter 4 Result Expression
Section 1 Expression of Reverberation Time
Article 4.1.1 The average value and standard deviation of the reverberation time for each measurement frequency at the measurement point shall be calculated, and the reverberation time frequency characteristic table shall be listed according to the octave center frequency.
For halls with relatively uniform reverberation time distribution, the corresponding reverberation time frequency characteristics and standard deviation can also be given according to the average value of each measurement frequency in the whole venue. The average value shall be calculated to the second decimal place according to the digital rounding rules. Article 4.1.2 When expressing the reverberation time with a curve graph, the frequency shall be given in logarithmic scale on the horizontal axis and the time shall be expressed in linear scale on the vertical axis in accordance with the requirements of the current national standard "Scale and size of drawing frequency characteristic curves and polar coordinate diagrams". The scale ratio of 1 octave to 1 second should be 3:4, and the length of 10 times (i.e. the frequency ratio is 10:1) should be 5 cm, and the points in the figure should be connected by straight lines. Section 2 Contents of the measurement report
Article 4.2.1 The reverberation time measurement report shall include the following contents; and shall be prepared in accordance with the requirements of Appendix 2 of this specification.
1. The location and name of the measurement hall;
2. Measurement items, measurement units, measurement date and main measurement person; 3. Hall volume, volume per seat and internal surface area; 4. Number of seats and material type. If it is a soft chair, the material type should be stated; whether it is turned up or laid flat during measurement; when the venue is full, the audience seat occupancy situation should be stated. 5. The orchestra pit is open or closed, and the fire curtain or curtain is hung or lowered; 6. Draw the plan and longitudinal section diagrams of the hall in proportion, and mark the location of the measuring points; 7. The layout of the interface materials in the hall and the interior decoration (including the quality of the stage curtain, the curtains of each door, the stage, the reflector and the orchestra pit) and the placement during measurement; 8. The temperature and relative humidity in the room during measurement; 9. The type of sound source or the type, model and placement of the sound source equipment and instruments. If it is a band, the specific number of people or the floor area should be given, and the stage furnishings and stage reflector should be explained; 10. The type and model of the recording instrument used. If a recorder (tape recorder) is used for recording, it should be specifically stated; 11. The measured reverberation time frequency characteristic table and frequency characteristic curve; 12. Measurement block diagram.
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