Audio Industry Standard
The measurement method of the maximum sound pressure level for the sound expansion of the hall
The maximum sound pressure level is an important index of the hall's sound reinforcement characteristics. The effective version of the GB is the GB/T 4959-1995 "measurement method of the hall's sound reinforcement characteristics". The standard specifies the definition and measurement method of the maximum sound pressure level.
Definition: the highest steady quasi peak sound pressure level produced by the sound expansion system at the auditorium listener's audience; four kinds of measurement methods include: electric input method (narrow band noise method), electric input method (wideband noise method), sound input method (narrow band noise method) and sound input method (broadband noise sound method).
The four method is basically the same as the signal source, and the measurement and data processing methods are basically the same.
One of these methods is described in this way: the 1/3oct (or 1/1oct) pink noise signal is fed directly into the input of the sound amplifying system, adjusting the output of the noise source, so that the input voltage of the loudspeaker system is equivalent to 1/10 to 1/4 to design the level of the use power. When the sound pressure is close to 90dB, it can be less than 1/10. The use of power. In the transmission frequency range of the system, the sound pressure level of each 1/3oct or 1/1oct band is measured and converted to the maximum sound pressure level of the corresponding frequency band and then averaged.
The proposal of the problem
A. what is the "highest steady quasi peak sound pressure level"? There is no clear definition in the GB, and how to measure it is even more impossible.
B. "detecting the sound pressure level of each 1/3oct or 1/1oct band and converting it to obtain the maximum sound level of the corresponding frequency band" is also somewhat ambiguous. What is the corresponding frequency band? There is no clear explanation of how to convert.
When the input voltage of C. speaker is more than one, how to determine the level of design power? When the maximum sound pressure level is measured from the level of 1/10 to 1/4 or less, how can we calculate the maximum sound pressure level when the maximum working power is measured? Even if it can be converted according to theory, what is the difference between the actual value and the theoretical value? In short, the maximum sound pressure level of the sound reinforcement system is not simply related to the input level or power of the loudspeaker system.
It is precisely because of the obvious uncertainty in the definition and measurement methods of the national standard that the understanding is not uniform, and the actual measurement is also inoperable.
Related discussion
On the definition
From the literal understanding of the maximum sound pressure level, it should be the sound pressure level generated by the maximum radiation energy in the normal working range of the sound reinforcement system, and it is the concept of peak value. Since the measuring equipment usually uses the effective value detection, it is the measurement of the effective value, so the effective value of the measurement results should be converted into the peak value as the expression of the maximum sound pressure level. The peak factor of sinusoidal signal is 1.4, and the peak factor of language and music is higher than that of sinusoidal signal. Therefore, the peak value in general condition should be above 3dB.
A definition of the maximum sound pressure level can be seen from the GB50371-2006 code for the design of the auditorium sound expansion system, which was implemented in 2006, and the correctness of the above understanding is demonstrated. The definition of GB 50371-2006 is as follows: "after the sound reinforcement system is debugged, the average maximum peak pressure level of each measuring point in the hall" is adjusted. If the revised GB4959 can adopt a similar definition, the problem of the uncertainty of the definition of the maximum sound pressure level will be solved.
On the method of measurement
The regulations of the national standard are not detailed enough. In addition to the question of how to synthesize the conversion and whether the actual value can be calculated with the theoretical value, the state control of the mixer has no corresponding regulations. It is obvious that there are problems in the operation of the measurement and the consistency of the measurement results.
Actual operation
Combined with our understanding and understanding of the maximum sound pressure level, in order to meet the requirements of the national standard to the maximum extent, in actual operation, the measurement process for the method one specified by GB/T4959-1995 is as follows:
A. put the sound reinforcement of the sound reinforcement system in the maximum state of the normal working range.
B. sound source adopts pink noise, and 1/3oct filter is used to directly measure the sound pressure level in each 1/3 band of each measurement point.
C. is converted to the sound pressure level of each measuring point in the audio frequency band (20Hz~20kHz) by converting the sound pressure level of the 1/3 frequency band of each measuring point.
The average measurement points of D. are averaged, and the average acoustic pressure level is obtained.
E. according to the peak factor of the sound source, the average sound pressure level plus the 20lg (peak factor) dB or the conservative estimation is directly added to 3dB as the maximum sound pressure level of the sound reinforcement system.
Because the peak factor of sound source also has the problem of measurement, sometimes the peak value is obtained according to the peak factor of conservative estimation as the maximum sound pressure level. GB50371 "hall hall sound system design specification" on the pink noise source peak factor is also a range: 1.8~2.2, the corresponding dB number is 5.1~6.8.
In addition, the sound expansion system will not be truly placed in the maximum state for other reasons, so it is suggested that the maximum sound pressure level of the sound expansion system is given in the form of more than or equal to dB, which is exactly the same as the design and rating requirements, and does not need to indicate the control position of the mixer.
∷
BADOOSOUND
BADOOSOUND
BADOOSOUND