Keywords conference hall; multimedia technology; noise; interference
Preface
As the name implies, multi-functional conference hall his function to be different from the simple conference hall, the diversity of functions determines his need to have a complex and numerous equipment integration, the following multi-functional conference hall equipment integration in the use of common problems to analyze.
First of all, the conference video display part, mainly by the projector, LCD TV, LED and other equipment, in use will often encounter multimedia display part of the signal is not stable, there are many sources of interference and other issues, mainly manifested in the projection screen jitter, unclear handwriting, etc., these are serious impact on the effect of the meeting, then the causes of these phenomena are what are the reasons for it? Electromagnetic interference: electromagnetic interference can be divided into power transformer interference and stray electromagnetic wave interference. According to the equipment installation site observation and analysis, the projector power supply must be used separately, three power grounding reasonable, the correct wiring method is to choose the main filter capacitor pins as a centralized grounding point, strong and weak signal ground line is strictly differentiated, in the total grounding point summary. Also important is the laying of the video line number line and access points need and speaker lines, power lines to maintain a certain distance, nearby try not to design and install high-power audio, high-power ballasts conference lighting equipment. These will interfere with the projector signal. Above this is a common problem in terms of video output. Then look at the sound output aspects of the common problems.
Second, the audio output part: by the computer, DVD, MD machine, workstation, mixer, microphone, amplifier, speakers, digital hard disk recorder, projector, LCD TV and other equipment. Realize the multifunctional hall on-site sound reinforcement, broadcasting, with the conference video system, to provide excellent audio-visual effects. In the operation of the equipment is often encountered in the use of the venue speakers should have encountered current interference and other inexplicable noise problems, there will also be speakers in the case of not connecting any sound source will also be issued noise, there is also in the use of the process of playing the file when the noise, and even the "inexplicable" noise, so that the The staff is at a loss. Water has a source of trees have roots, of course, the noise does not come out of nowhere, here we briefly introduce several kinds of multimedia speakers interfere with the sound of the reasons, share some easy to implement the solution, and we learn together. Generally speaking, large professional conference rooms will not be a large number of active speakers, only a simple explanation here, the amplifier will be stored in the active speaker chassis, so the noise will be there, absolutely no interference sound is impossible. Active speaker noise by source can be roughly divided into electromagnetic interference, ground interference, mechanical noise and thermal noise.
Third, the conference environment control system and intelligent multimedia central control system of the entire sound field and signal is also very obvious, the conference environment system controls the lighting of the conference room, the conference environment, the conference atmosphere. Central control system to achieve a multimedia conference room centralized control of a variety of electronic equipment; such a wide range of equipment integrated, will certainly have an impact on the conference sound, generally there may be from three aspects of the conference noise: one is the equipment itself noise; the second is the external electromagnetic wave interference noise; third is other power interference noise. Let's analyze together, the equipment itself inherent noise exclusion, microphone, DVD deck, mixer, effects, equalizer, pressure limiter, exciter, electronic crossover, power amplifiers, speakers and other equipment constitutes the sound system, a number of equipment may be the starting point of interference. To find, judge the noise is generated from which equipment components, it is necessary to check the noise of each device, you can use the method of elimination to find.
First turn on the audio equipment power supply, the order is in the order of the power-on signal flow step by step. There is noise coming from the speakers. You can turn off the wireless microphone receiver switch, check whether there is still noise coming out. If the noise continues, it proves that the noise is not generated by the wireless microphone receiver, and you can check the other equipment again. Then check the sound transmission gain knob of each of the other microphones, and if the noise disappears when you turn off the gain knob of a certain microphone channel, you can judge that the noise is generated by this road. If the noise still exists, you have to test other devices. Check the power supply of the DVD player, the general DVD power supply, audio and video lines are wired correctly to produce noise interference is unlikely. Check the power supply part of the mixer, then the noise disappears, it proves that the noise is generated by the mixer; still exists, it proves that the noise is generated by other equipment. Summarize the above links, mainly to check the status of interference after the switch of the main equipment. Then you can turn off the peripheral equipment in turn to check the power amplifier, electronic crossover, effects processor, exciter, compressor, equalizer, acoustic feedback suppressor and other peripheral equipment to turn off the power to check to see if the interference has changed. Turn off a device when the interference disappears, then prove that the interference is generated by this device.
Specific inspection, after the discovery of the equipment that generates interference, you can carry out a specific inspection of the structure of the body inside the box.
In the audio system by high-frequency radio interference, outdoor high-frequency radio waves is also the main source of interference, wireless microphone used in meetings, outside radio waves will cover the location of the venue, interference with the reception of the wireless microphone, and sometimes inducted into the radio station broadcasting sound. We recommend the use of self-tuning band wireless microphone, to avoid the interference of radio waves.
Bad grounding will also make the sound system interference into the next level of equipment. This also has certain technical requirements: the power supply ground connection must be separated from the sound system ground point, so as to avoid the interference of the power supply string into the sound system. Multi-stranded textile wire is the first choice of audio equipment grounding line, requires professional welding, grounding line resistance should be less than four ohms. Audio equipment can not be grounded at the same time as the input and output terminals, constituting a grounding wire loop, which is prone to generate magnetic fields. Grounding requirements at the input end of a single point of grounding, because the signal level at this point is small, the relative ratio of interference power is also the smallest. If the output point of grounding, the relative ratio of the signal power at this point is larger, the relative ratio of the interference signal power is also larger, so the elimination of interference is not easy to completely eliminate. Lighting high-power semiconductor device noise interference, some venues, suffered from power supply noise interference is the largest from the lighting high-power semiconductor device interference wave, because some professional lighting light and dark, strong and weak changes are not realized by changing the 0 ~ 220V voltage, but through the electronic circuit to control the high-power semiconductor device of the conductive starting point angle, the performance in the sound system, there is a clear interference Noise. In order to eliminate high-power semiconductor device interference noise, the most effective way is the three-phase power supply in the two-phase to provide for the use of lighting, one of the phase as a sound system dedicated. This will avoid the interference of high-power semiconductor devices for stage lighting.
Grid voltage instability will also interfere with the signal stability of the professional conference hall, in order to eliminate the interference of these external power supply. Introduces several applicable voltage regulator regulator tools, through the use of voltage regulators, voltage regulators, isolation transformers, magnetic saturation regulators, with filtered power supply and other such practical tools can help us to use the voltage adjustment in the precise range of two hundred and twenty volts within the grid power supply to play a purifying role, due to the regulator's electromagnetic circuit, can be eliminated to a certain extent the power supply of the noise to be eliminated, thereby improving the sound system tone quality level. Sound system sound quality level.
The development of conference media technology in recent years has brought new thinking and new opportunities for technicians within the conference audio profession. The continuous development and maturity of digital automation technology, so that its application is constantly expanding, can be widely used in conference security work. Practice has fully proved that the professional conference room equipment integration is a comprehensive technical problems, technicians only in the continuous research and exploration, improve the technical level.
References
[1]Sun Jianjing. Modern Audio Engineering, April 2008
[2]Li Hongbin. Audio Technology and Tuning Techniques, January 2006
[3]Yang Stackyun. Electronic Devices: From Principle Analysis to Troubleshooting and System Applications, January 2008