1. When the public address system does not whistle, it can be considered as an open-loop sound reinforcement system, without considering the sound gain. On the contrary, if the system will produce an acoustic feedback whistling, it can be considered as a closed-loop sound reinforcement system. At this time, the microphone is used to amplify the sound, and the system gain cannot be increased arbitrarily while maintaining the stability of the system. Therefore, it is necessary to evaluate the transmission of the system. Sound gain.

2. The core of the acoustic characteristics of the public address system is to ensure that the volume is sufficient and the reverberation is clear.

3. The so-called volume is sufficient relative to the ambient noise, usually the signal to noise ratio must reach 12 ~ 15dB. However, if only the signal-to-noise ratio is specified and the sound pressure level of the system is not regulated, it will be difficult to operate. Because the ambient noise of the broadcast service area is subject to change at any time, it cannot be simply based on the measurement of the working hours.

4. For the sound pressure level of emergency broadcasts, in addition to the minimum level that must be met, the noise level at the site in the event of a public emergency must be estimated to determine the level at which the sound pressure level should be achieved. .

5. The volume is sufficient to reproduce the sound, but it is not a sufficient condition. Distortion, transmission frequency characteristics, reverberation time, early and late sound energy ratio, etc. all have an important influence on the playback sound resolution. Since the acoustic environment of the public broadcasting service area is quite different from that of the halls and professional venues, this specification directly specifies the language definition (or the sound reinforcement system language transmission index) for ease of operation.

6. Considering that the public broadcasting system not only reproduces speech sounds, the transmission frequency characteristics and the signal-to-noise ratio of the system equipment, which have an important influence on the sound quality, are also regulated. The number of broadcast speakers used in public address systems is usually large, and the same broadcast service area may cover different environments, so it is not necessarily convenient to use the equalizer; at the same time, the price level of the broadcast speakers is much lower than that of the professional speaker system of the same grade. Therefore, the transmission frequency characteristics of the system are appropriately relaxed compared with the professional halls and venues.

7. The specification of leakage sound attenuation is mainly to guide the designer to maximize the sound power resources for the broadcast service area and to limit the interference of the broadcasting system to the service area.

8. Since the outdoor service area of the public address system is complex and the scope may be very broad, this specification does not require the sound field uniformity and transmission frequency characteristics of the outdoor broadcast service area. In fact, under the premise of ensuring a certain sound pressure level and speech intelligibility, the sound field uniformity and transmission frequency characteristics are not very important for the outdoor broadcast service area. Conversely, for different locations of the same broadcast service area (especially outdoor), the background noise may vary widely, so it is reasonable to provide different broadcast sound pressure levels instead of uniform sound pressure levels for these different locations.

9. The acoustic characteristics specified in this code are based on the current economic situation in China and are formulated according to needs and possibilities. In the preparation process, this specification refers to the acoustic characteristics of halls and venues such as GB50371 and JGJ/T131. Considering the coverage of the public broadcasting system, the acoustic environment, the equipment, the investment, and the user's appeal, there are many differences in the sound reinforcement systems of the halls and venues, thus making different provisions.