Development and prospect of conference sound reinforcement system
2018 is the 40th anniversary of reform and opening up. After nearly 40 years of development, China's professional audio and lighting industry has gradually realized leap-forward development from imitation to innovation, from OEM to brand. On major projects such as the BRICS Conference, the G20 Summit, and the Expo, more and more people have seen the Chinese national brand, and the world has heard the voice of China.
I. Overview of the conference sound reinforcement system
The application of the conference audio sound reinforcement system covers almost all daily activities such as foreign affairs reception, news release, technical forum, conference exchange, etc. Therefore, the conference sound reinforcement system has become an indispensable construction content, and sometimes even becomes an important part of the completion acceptance of the entire project. section.
There are many forms of meetings: speech, report, discussion, and teleconference. Due to the different number of participants, the size of the venue is different, the functional requirements are different, and the conference sound reinforcement system will vary widely and in different forms.
The function of the conference system is perfect. Not only the venue environment should pay attention to the aesthetics of the decoration aesthetics, but also the practical function of audio-visual effects. The beautiful decoration and the sound quality can make the audience enjoy the spirit.
The most important part of the conference system is practical reliability. In the meetings before the 1980s, because of the limited conditions, the information dissemination method was single, and only the language reinforcement was considered. That is to say, the speaker's voice is amplified by sound amplification, so that more people can hear it.
After the 1990s, with the popularization of multimedia technology, the large screen was widely used as a display means in the conference, and the playback of related audio and video materials was also used more and more in the conference. Therefore, the conference system should not only consider language sound reinforcement, but also consider the playback and storage of audio and video signals.
With the development of the times, people are increasingly pursuing high-level and high-quality! Psychoacoustics tells us that people's perception and appreciation of sound has a development process from low-level to high-level, from perceptual to rational, and the listener is perceiving sound effects. In the process of thinking, the outer image and inner image of the sound are gradually established. The perception of these images affects people's thinking and judgment of sound unconsciously. The superficial image gives the listener a stimulus, and the inner feeling gives the emotion. Change, this is the connotation of psychology.
Therefore, the development goal of the conference sound reinforcement is to convey the feelings of the speaker. It is not only through the speaker's language content as a carrier, but also conveys the feelings expressed by the speaker's language more appropriately to the audience, and truly makes the speaker's voice reach the effect of infecting the listener's emotions.
However, some people think that the technical difficulty and requirements of the conference-type sound reinforcement are not high. I feel that the conference sound reinforcement system is very simple, and it does not pay attention and research. The venue presents generality and regularization. The sound reinforcement of the actual conference sound has its particularity and complexity, and it implies a lot of technical difficulty.
Second, the basic knowledge of the conference sound reinforcement system
The human voice is mainly caused by the vibration of the vocal cords. The language is characterized by intermittent and transient, and its pitch and timbre are determined by the fundamental frequency of the language itself and the harmonics. The density of sound energy in Chinese is generally concentrated. Distributed between 200Hz-700Hz, the male vocal cord is longer and thicker (that is, the structure of the sound source itself), the pronunciation frequency is lower, and the average basic frequency (the pitch-male bass average) is about 230Hz (bass singer fundamental frequency) Can be as low as 60Hz soprano fundamental frequency can be as high as 1kHz). The harmonic frequency generated by the speech is up to 6 kHz, the sound pressure level is 60-70 dB, and the dynamic is 80 dB.
The characteristics of Chinese, the tone is swaying, and the logical accent changes are large and varied. Poetry or essays are catchy, rhythmic, powerful, and rhythmic. Chinese sentences, accent, tone, and rhythm, we must analyze the speaker's pronunciation characteristics, but also analyze the frequency, adjust the voice with high and low frequency, and get the best sense of hearing. The sound of Chinese, because of the different sound belts, the gap between men and women is large, between men and men, between women and women, the pronunciation energy of Chinese is concentrated at 200Hz-700Hz, which is a medium-low frequency, so pay attention to male voices. Thickness, pay attention to the female voice, do not mix low frequency, medium frequency is not hard, high frequency is not sharp, giving people a full, bright and natural feeling.
In other words, the human voice can meet the needs of listening clearly in the range of 100 Hz to 1.2 kHz. Plus all kinds of harmonics, understandable pure voice, only need 200Hz ~ 3.5KHz, the upper limit of the bandwidth of the telephone is 4KHz; the upper limit of the broadcast of the TV is 8KHz; the bandwidth of the HD conference call is about 8KHz. It can be seen that in the language transmission range, it is not necessary to increase the bandwidth requirement without limitation, because the bandwidth increase may cause many other negative effects such as transmission burden and phase interference.
The main objectives of the sound system design include “resonance” and “sound reinforcement”. This is the first thing that happens in the natural environment and is bound to be affected by the natural environment. The figure shows the flow of a common small sound reinforcement system. . We need to analyze the links that are prone to different quality changes before we can come up with realistic design solutions and achieve excellent results.
Third, the technical requirements of the conference sound reinforcement system
The sound reinforcement of the conference before the 1980s was "listen". In the 1980s and 1990s, it was "understand and heard clearly." After entering 2000, the requirements for the conference system were "hearing well and listening comfortably." ", there are strict requirements and evaluation of language clarity.
If you focus on the design of speech intelligibility at the beginning of the system design, and pay attention to the improvement of the sound gain, there will be a qualitative leap in the concept of the whole system, such as coordinating the entire sound field environment and electroacoustic system. Design can create a quality project.
As we all know, the microphone and speaker in the conference system are in the same sound field. The feedback suppressor in the past peripheral devices is configured with: frequency shifter, phase shifter, notch filter, equalizer, etc. The signal is distorted (even odd, not good). At present, the anti-howling processor is adopted, which converts the passive type into an active type, and uses a powerful DSP system, which has a fully automatic detection of the site whistle point function, automatically adapts to the acoustic environment, and actively filters out the howling signal that causes the acoustic feedback. And eliminate it before the acoustic feedback occurs, and the original signal is not damaged, which is a big step forward for peripheral equipment.
The conference sound system is mainly language sound reinforcement, and the most important indicator is language clarity. It is known that the speech intelligibility is highest at the sound pressure level of 65 to 85 dB, so it is appropriate to control the volume of the venue to be around 75 to 80 dB, and the meeting can be held easily and happily.
We refer to the speaker parameters: sensitivity is above 90dB (lm / 1W), which means that only a small amount of power to push the speaker can get enough loudness for the conference system. In actual bidding applications, high-power amplifiers and high-powered speakers for performances are often used as equipment for conference sound reinforcement. Not only are resources was wasted, but they are always in an under-working state, resulting in a lack of sound quality.
According to the special needs of the conference sound reinforcement system, digital power amplifiers (100W ~ 200W) adapted to the use of the conference system have been developed. No matter the volume is large or small, the sound quality is soft, clear and bright. sound.
Fourth, the conference audio sound system design essentials
The conference audio sound reinforcement system has been developed to the present day. From the concept of venue system design, the following points should be promoted:
1. Jiansheng decoration bears the brunt. Many people in this area know that there is such a thing, but they tend to pay less attention to it. The one-sidedness is limited by the aesthetics of the decoration. The “sound decoration” and the “ordinary decoration” are mixed together (some decoration designs do not understand the sound design technology at all). ), made a "compromise" against scientific principles. The topic of Jiansheng decoration is very big. I only say 20-word policy here--"frontcourt reflection, midfield diffusion, backcourt sound absorption, ceiling strong suction, door and window soundproofing", concise and concise, you may wish to try.
2. Microphone noise reduction technology application. With the passage of time, there are more and more environmental noises, some are audible, some are electronic pollution, which seriously interferes with the normal operation of the conference sound reinforcement system. In the past two years, audio workers have proposed system noise reduction and strive to improve S/N. In particular, the noise cancellation of the microphone pickup signal, the signal quality is greatly improved, and also provides conditions for long-distance pickup, the speaker can speak freely away from the microphone. The hanging wheat that came into being came into being rapidly developed. The clear voice can be picked up in the range of about 5 meters, and the technical guarantee for the desire of "the microphone can not be seen at the venue".
Of course, noise reduction is a digital processing technology. Don't be fooled into it. Turn the original signal into a distorted signal, which is difficult to hear.
3. Reasonable layout and angle adjustment of the speaker. The speaker and microphone should be installed in a back-to-back relationship, avoiding the other axis, and using the principle of low directivity of the speaker and the directivity of the directivity of the microphone to improve the sound gain and ensure the quality of the venue. At the same time, each speaker directly covers the designed area, avoiding the sound energy directly radiating to the large surface of the nearby wall surface, ceiling, etc., to improve the language clarity.
4. Use new technology for intelligent control. With the development of digital technology, sound field processing equipment has presented diversity, citing new technologies and new products, abandoning the common frequency shifting and trapping objects as feedback suppressors, and improving the comfort of the venue. The anti-howling sound processor is adopted to push the conference sound reinforcement system to be more stable and reliable, and the management is simpler and the effect is more warm. Design a variety of work modes to achieve one-click management, so that each use function can achieve the desired goals, achieving comprehensive and excellent results.
5. Use digital processing for intelligent control. A lot of modules are built into the digital audio processor and can be used. For example, the AGC module can automatically balance the volume to a large extent, without manual operation, and finally realizes an "unattended" conference sound reinforcement system.
6. Language clarity has become an important technical indicator for testing and acceptance. Speech intelligibility is a physical quantity that measures the degree to which a speaker's speech is understandable. The test process is extremely simple and the results can be accurately tested in 15s. Conference speech sound clarity: The national level indicator is STIPA ≥ 0.6, and our engineering design acceptance should exceed this indicator.
V. Outlook audio sound reinforcement system outlook
In addition to the audio sound reinforcement system, the conference system will also involve video technology, lighting technology and network transmission technology. The conference audio sound reinforcement system, its development must be intelligent and integrated. Integrate audio sound reinforcement with multimedia video, even conference documents, office OA systems. At present, the excellent domestic manufacturers have completely stood in the world in this respect, and the products have reached or exceeded many products of international famous brands. We should abandon some old-fashioned autism ideas, boldly apply domestically produced quality products, and innovate and develop more intelligent building quality projects.
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