Under the influence of environmental noise, the propagation distance of sound source is reduced. Therefore, in addition to conventional concert halls, opera houses, and theaters, some public activity places can use electroacoustic technology to amplify sound, amplify the sound source signal, and improve the sound pressure of the listening area to ensure that each audience can get the appropriate sound pressure level. In recent years, with the rapid development of electronic technology and electroacoustic technology, the sound quality of acoustic sound reinforcement system has been greatly improved, which can meet the continuous improvement of people's requirements for sound quality.
Amplification sound system is also called professional sound system. There is a common misconception that sound reinforcement systems are very simple, and only need to connect microphones (and other sound sources), mixers, amplifiers, and speakers to form a sound reinforcement project. This understanding has led many owners to invest a lot of money, the available language amplification effect is fuzzy, the interference of feedback screaming makes the sound can not be turned on, and the sound quality becomes tasteless when the music is replayed.
Sound reinforcement system is a system engineering, it involves electronic technology, electroacoustic technology, building sound technology and acoustic art and other disciplines, but also needs to be closely coordinated with the video system (multimedia projection and camera system), stage or ballroom lighting system, fire broadcast system, paging broadcast system and security system and other subsystems. The sound quality of the sound reinforcement system is not only related to the comprehensive performance of the electro-acoustic system, but also related to the sound propagation environment - the use of building acoustics and field tuning. The function and sound effect of the sound reinforcement system need the best cooperation of correct and reasonable electroacoustic system design and debugging, good sound transmission conditions and correct field tuning technology. The electronic sound system is like a car on the road, the audio equipment is like the road, and the tuner is like the car driver. The performance of the car is a necessary condition for safe and fast driving, the quality of the highway road surface is an important basis for achieving vehicle balance and fast driving, and the driving technology and experience of the driver is the basic guarantee of driving safety. Third, they complement each other and are indispensable.
As a system problem, the sound reinforcement system must consider the above problems comprehensively in the system design. Through careful system design, meticulous system debugging, good sound conditions, on the basis of the selection of good performance of electroacoustic equipment, to achieve a pleasant natural sound effect.
First, sound reinforcement system classification
The general sound reinforcement system includes two categories: sound reinforcement system and sound reproducer system:
1. Sound reinforcement system: the speaker and the microphone are in the same sound field, and there are whistles, distortions and oscillations caused by sound feedback and room resonance. In order to ensure the stability and normal operation of the system, the maximum system gain is reduced by 6 dB compared to the critical gain for acoustic feedback self-excitation.
2. Resound system: the system only has tape drives, optical disc players and other sound sources, no microphone, silent feedback is possible, and the acoustic feedback coefficient is 0, which is a special case of the sound reinforcement system.
Sound reinforcement systems can be divided into the following categories according to their use:
1. Outdoor PA system
Outdoor sound reinforcement system is mainly used in stadiums, stations, parks, art squares, music fountains and so on. It is characterized by large service range, wide space and large background noise. Sound transmission is mainly direct sound; The sound pressure level is required to be high, such as around high-rise buildings and other acoustic reflection objects, the speaker layout is unreasonable, the sound wave is reflected several times and forms a delay of more than 50 ms, and there will be serious problems such as echo. In the outdoor system, it will also be affected by climatic conditions, wind direction, environmental interference and other factors.
2) Indoor sound system
Among them, the most widely used is the indoor sound reinforcement system, including various cinemas, stadiums, dance halls and so on. Its professionalism is very strong, not only can provide a sound source for various artistic performances, but also has high requirements for sound quality. The design of the system should consider not only electroacoustic technology, but also the sound quality of the building. Indoor shape and other factors have great influence on sound quality.
3) Motorized performance system
In addition to the fixed installation system, the sound reinforcement system also includes the flow system. Various large venues temporarily installed for non-artistic performances [such as stadiums (gymnasiums), art broadcasts, large banquet halls, etc.] are called mobile performance systems. The mobile performance of the sound equipment must be compact, easy to carry, transport and installation, high reliability, can adapt to a variety of harsh use environment. Large flow system investment is large, generally leased to professional audio companies.
4) Public address system
The public broadcasting system provides background music and radio programs for hotels, commercial buildings, ports, airports, subways, and schools. In recent years, the public address system also serves as an emergency broadcast, which can be linked with the fire alarm system. In the public address system, there are many control functions, such as area broadcast, all call broadcast, forced switching, priority broadcast and so on. Loudspeaker load is large and dispersed, and the transmission line is long. In order to reduce transmission line losses, 70 V or 100 V constant voltage high impedance transmission is generally used. The sound quality is not too high, and the sound quality is mainly alto and midrange.
5. Conference system
In recent years, with the increase of communication at home and abroad, teleconferencing, video teleconferencing and digital conference system (DCN) have developed rapidly. The conference system is widely used in conference centers, hotels, conglomerates and government agencies.
The conference system mainly includes the conference discussion system, the voting system, the simultaneous interpretation system and the video conference system. This system requires audio, video (image) system synchronization, and computer control, storage.
Second, sound reinforcement system design
The design of the sound reinforcement system generally starts from the sound field, and then enters the power amplifier, sound processing system, mixing table, until the microphone and other sound sources. The design step is the only way to gradually move backwards. As the sound field design is the basis to meet the system function and sound effect, it involves the selection of speakers, sound supply scheme and signal path. It is necessary to determine the speaker system to calculate the power amplifier drive power and determine the driver signal path, and then further determine the signal processing scheme and the choice of sound platform according to the distribution scheme of the drive power.
Sound field design is the basis of sound reinforcement system, which involves the sound effect of the whole system, but it is also a very heavy work. With the rapid development of computer technology, it is now possible to use acoustic software tools above EASE3.0 for calculation, and finally obtain sound field design reports that meet the expected requirements [1] and [2]. In order to achieve the requirements, the sound field design process needs to be repeated several times.
Tape voting or simultaneous interpretation systems can be configured according to different meeting needs.
To vote, delegates simply press the vote button on the device in front of them, and the vote result will be displayed on the LCD screen of the chair machine, or on other screen display devices in the conference room via CCU and DCN software.
Simultaneous interpreters usually use 1+3 (one mother tongue and three target languages), and can add seats for spectators when needed, but other seats than official representation.
Languages can be assigned either wired or wirelessly:
Wired language allocation The cable trunk of the DCN system is used to assign the translated language to the conference participants. Official delegates listen to the translated language through earphones connected to the speaking equipment equipped with a channel selector, and non-delegates listen to the translated language through earphones connected to the channel selector
Wireless transmission with infrared system to achieve wireless transmission
A typical infrared system includes infrared transmitters, radiators, and personal infrared receivers:
Infrared transmitter: Each language channel has a carrier
Infrared radiation: Used to distribute infrared signals throughout the site.
It can be inserted into the wall or ceiling during installation. The optimal infrared signal coverage in the field can be obtained by adjusting the installation position of the radiator properly.
Infrared receiver: can receive up to 16 language channels, with high-speed conversion channel function, LED display and voice amplification function.
The conference acoustic reinforcement system is briefly described