The public address system is a systematic project, which requires the close cooperation of various disciplines such as electronic technology, electro-acoustic technology, acoustic technology and acoustic art. The sound effect of the public address system is not only related to the comprehensive performance of the electro-acoustic system, but also to Sound propagation environment Architectural acoustics and on-site tuning are closely related, so the final effect of the public address system requires the cooperation of correct and reasonable electro-acoustic system design and debugging, good sound propagation conditions and correct on-site tuning technology. Complement each other is indispensable. The above problems must be comprehensively considered in the system design. On the basis of selecting electro-acoustic equipment such as PA loudspeaker with good performance, through careful system design, careful system debugging and good acoustic conditions, the electro-acoustic pleasant and natural sound effect can be achieved.
Introduction to the function of public address system
The public broadcasting system should have background music broadcasting, public service broadcasting, and firefighting functions. It is used in office areas, corridors, elevator halls and other areas. Usually, background music can be played in public areas. It can be played manually, automatically in a loop, or played regularly. When a fire occurs, it can also be used as an accident broadcast to direct evacuation. The design of the system must consider the characteristics of the place of use, the noise level, the size and height of the space, and determine the number of speakers according to the speaker's diffusion angle, sound pressure level and rated input power. The main function of the background music system is to cover up the noise and create a relaxed and harmonious listening atmosphere. The speakers are required to be dispersed and evenly arranged, with no obvious sound source directionality, and the volume is appropriate, so as not to affect the normal conversation of the crowd; the volume of the background music should be higher than the scene. The noise is about 3dB. Generally, public broadcasting should be set up in the following places: elevator halls and stairways, offices, toilets, etc., among which the volume of the office can be adjusted or turned off according to the requirements, and the volume can be reached during emergency broadcasting. The public broadcasting system can be used for regular broadcast of fixed programs, publicity, broadcast notification, finding people, etc., and plays the role of broadcast evacuation in emergency situations. This function requires that the sound field intensity of the sound reinforcement system is slightly higher than that of the background music. Based on the principle of not affecting the speech between the two people, the volume of the public broadcast is about 10dB higher than the live noise. The fire accident broadcasting function is used as a broadcasting facility for the fire alarm and linkage system to command and evacuate the crowd in an emergency. The crowd in the area that may be involved in the object can clearly hear the voice of alarm and guidance.
Today's public broadcasting integrates playing background music, publicity, paging broadcasting and emergency broadcasting of fire accidents. This is a very versatile broadcasting system, most of which have the following functions and technical requirements:
1. Play background music and play paging
Background music is referred to as BGM (Back Ground Music), its function is to cover up the ambient noise in public places and create a relaxed and pleasant atmosphere. The average sound pressure of background music is around 60 to 70db.
2. Emergency broadcast
In the past, the emergency broadcast system was combined with the fire alarm system as an independent system, but later it was found that because the emergency broadcast system was not used for a long time, its reliability was often a problem, but it became dumb when it was officially used. Now the fire alarm system and the background music system are integrated together to form a highly versatile public address system.
3. Priority broadcast right function
When a fire occurs, the fire-fighting broadcast signal has the priority broadcast right, that is, the use of the fire-fighting broadcast signal can automatically interrupt the background music and paging to find people and other broadcasts.
4. Constituency broadcasting function
When a fire alarm occurs in the building, in order to prevent confusion, it only broadcasts to the fire area and its adjacent areas, directs evacuation and organizes emergency calls. This selection function should include automatic selection and manual selection to ensure reliable execution of instructions.
5. Forced switching function
When playing background music, the input state of each speaker load is usually different, and some are in a low volume state. Some are turned off, but during emergency broadcast, the input state of each speaker will be turned to full volume state, that is, the volume will be forced to switch through remote control commands.
6. The fire duty room must have an emergency broadcast console, which should be able to remotely control the startup and shutdown of the public address system. The sub-console microphone has priority playback, and the sub-controller has strong switching rights and constituency broadcasting rights, etc.
