How to eliminate the noise phenomenon in common sound reinforcement systems
The sound reinforcement system consists of sound reinforcement equipment and sound field components, including the sound source and the acoustic environment around it, the microphone that converts the sound into electrical signals, the equipment that amplifies the signal and processes the signal, the transmission line, and the speaker that converts the signal into an acoustic signal. And the acoustic environment of the audience area. It is also a means of processing the original sound so that the listening effect achieves the desired effect.
There are many problems in the use of the sound reinforcement system. The audio noise is the most troublesome. The three common aspects are the noise generated by the power supply equipment, the noise generated by the external electrical equipment and the noise of the system itself.
Noise generated by the power supply
This phenomenon occurs mostly in a variety of equipment public power supply. Some adjustable light changes are not realized by changing the voltage. Instead, the electronic circuit is used to control the conduction rate of the thyristor, and the output power is controlled by the method of controlling the area of ​​the alternating current waveform. Thereby changing the light and shade. This method causes noise in the sound reinforcement. In response to such a phenomenon, it is recommended that the lighting use circuit be used separately from the sound reinforcement system.
The occurrence of clutter in the power grid can also cause such a situation, because our household electricity and industrial electricity are connected in parallel in a system of the national grid. Larger amounts of electricity used in industrial electricity can lead to voltage drops and unpredictable sources of noise.
In this case, a voltage regulator can be combined with a regulated power supply to solve the power supply noise problem. The voltage regulator maintains the voltage at 220 V, and the electromagnetic circuit in the voltage regulator can also eliminate some noise waves in the power supply. In addition, the regulated power supply makes the adjusted voltage relatively stable, and the voltage fluctuation can be corrected to the normal range in time.
Noise generated by external waves
For the noise phenomenon that is easy to occur in wireless devices, many of the devices we use now are connected by wireless signals, which is easy to interfere with each other. Therefore, when using wireless audio devices, we must first check the transmission and reception of wireless devices. The frequencies can be adjusted to each other, which can effectively avoid frequencies that are not wanted.
Selecting a wireless microphone that can operate in the UHF (Ultra High Frequency) band will have a lower chance of problems. The grounding point of the sound system must be independent (not shared with the power supply). If the input end of the system is grounded, the output terminal is also grounded, the noise signal has been amplified, it is not easy to eliminate, and because the input and output terminals are equipotential, it is easy to generate feedback.
System inherent noise
In the sound reinforcement system, various audio processing peripheral devices are provided, and the devices cooperate with each other to better assist the tuner to complete the sound reinforcement task, and on the other hand, the connection of multi-level devices is also easy to generate electrical noise and influence. The quality of sound reinforcement work. For this situation, the tuner is required to have a strong judgment and to accurately identify which level of system noise comes from.
Screening and discriminating, noise appears at startup, first cut off the power of the microphone receiver, if there is still noise, it can be eliminated;
Then turn off the CAIN knob through the channels on the mixer to find out where the noise is on the road. If all the input channels are off and there is noise, proceed to the next step;
Turn off the mixer's power supply, thus troubleshooting the entire console including bus, grouping, return, auxiliary, master control, intercom and oscillation;
If there is noise, check the peripherals, such as exciters, compressors, feedback suppressors, equalizers, dividers, effects, and amplifiers. This work is very tedious, and it is necessary to judge one by one, and then determine which device the noise comes from before processing.
“The feedback whistle must not appear during the conference or speech. The tuner should mark the whistle on the mixer and keep a safe distance from it.
The best sound amplification area should be based on the position of the main stage. The effect of listening here should be guaranteed. The sound engineer should listen to these positions before the performance, and understand how the backup power will be provided in an emergency. The contact person in charge of the on-site power supply should immediately adopt the correct treatment method in case of power failure, and strive to minimize the loss.
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