The outdoor broadcasting system is mainly used in places such as stadium, station, park, art square, music fountain and so on. It is characterized by its large service area and wide space. Its background noise is large. The sound transmission is the mainly direct sound transmission, and the required sound pressure level is high. If there are high buildings and other reflective objects around it, the layout of the loudspeaker is not reasonable, and the sound waves are reflected for many times causing a delay of more than 50ms, which will cause double, multiple sounds and even echo, affect the clarity and the sound image positioning. The acoustics of outdoor systems can also be affected by climatic conditions, wind direction, and environmental disturbance.
The indoor broadcasting system is the most widely used system, it includes all kinds of movie theaters, sports venues, dance halls and so on. Its professionalism is very high. It can not only amplify non-languages but also be used for various kinds of theatrical performances. Its requirement for the sound quality is very high. The electroacoustic technology, as well as the architectural acoustics, should be taken into consideration during the system design. Besides, factors like the shape of the room have a great impact on the sound quality.
The public cordless pa system provides background music and radio programs for places like hotels, shopping malls, ports, airports, subways, and schools. In recent years, the public address system is also used for emergency broadcasting, which can be linked with the fire alarm system. The public address system has many control functions, such as region broadcast and whole area broadcast function, mandatory change function and priority broadcasting function. The loudspeaker is much loaded and dispersed, and the transmission line is long. In order to reduce transmission line loss, 70V or 100V constant voltage and high impedance transmission are usually used. The demand for sound pressure is not very high, and the sound quality is mainly the middle and the alto pitches.
With the increase of domestic and international exchanges, telephone conferencing, video conferencing and digital conference system (DCN) have developed rapidly in recent years. The conference system is widely used in conference centers, hotels, groups and government agencies. The conference system includes a conference discussion system, a voting system, a simultaneous interpretation system, and a video conferencing system. The system requires the synchronization of sound and video (image) systems, and the conference data is controlled and stored by the computer.