1 the specifications set forth by the acoustic characteristic indices, according to current situation of our country economy, from the necessity and possibility of starting to develop. This specification is in in the process of making reference to GB50371, JGJ / T131 and other relevant hall, stadium acoustical characteristics. Considering the public broadcasting system coverage, acoustic environment, equipment, investment and user requirements etc, with Hall venue PA system, there are a lot of differences, which made distinct from their provisions. 2 acoustical specifications for public address system core, is to ensure that the volume and playback voice clearly enough.

The 3 volume is called enough relative to ambient noise, signal-to-noise ratio, is usually required to achieve 12 ~ 15dB. But if only the signal to noise ratio provisions and non-standard system ensured sound pressure level, it would be difficult to operate. Because broadcasting service area environmental noise is always changing, not simply to measure the operation time as according to.

4 for emergency broadcast sound pressure level, except must reach the minimum limit, it must also be in case of sudden public incident spot noise level estimation, to determine its ensured sound pressure level should reach the level of.

The 5 volume is sufficiently heavy to clear the conditions necessary, but not sufficient condition. Distortion, frequency transmission characteristic, reverberation time, sound energy ratio on early and late sound clarity has important implications. As a result of the public broadcasting service area of the acoustic environment and hall and professional venues differences, for ease of operation, the code directly on speech intelligibility ( or PA system speech transmission index ) provisions.

6 considering the public broadcasting system not only reproducing voice, so the quality has an important effect on the transmission frequency, ratio of system is also provided. Public broadcasting system using the radio speaker volume is usually higher, but also with a broadcasting service area may be covered with different environments, so it is not necessarily easy to use equalizer; at the same time, the radio loudspeaker price levels are far lower than the same level of the professional loudspeaker systems. Therefore, the system transmission frequency characteristic with professional halls, stadiums, appropriate to relax the requirements.

7 standard leak out acoustic attenuation, mainly in order to guide designers as much as possible to maximize the sound power resources for broadcasting service area, while limiting broadcast system on service of outside interference.

8 as a result of the public broadcasting system outside the service area environment is complex, but can range is very wide, so the standard of outdoor broadcasting service area of the sound field uniformity and transmission frequency characteristic request. In fact, in the guarantee to have certain ensured sound pressure level and language the clarity of the premise, sound field uniformity and transmission frequency characteristic for outdoor broadcasting service area is not very important. In contrast, for the same broadcasting service area ( especially outdoor ) in different sections, background noise may have very big difference, therefore to these different areas with different broadcast sound pressure level rather than uniform sound pressure level is reasonable.

9 when the public broadcasting system won't squeaking, can be thought of as a ring opening reinforcement system, without considering transmission gain. Conversely, if the system will sound feedback whistle, it can be thought of as a closed loop of the PA system, then use the microphone PA, unable to maintain system stability under the condition of random increasing the system gain, so it is necessary to assess system transmission gain.