The feedback suppressor usually means that in the sound reinforcement system, if the microphone volume is greatly increased, the sound from the speaker will be transmitted to the whistling caused by the microphone. This phenomenon is the acoustic feedback. The existence of acoustic feedback not only destroys the sound quality, but also limits the extended volume of the microphone sound, so that the sound picked up by the microphone can not be reproduced well; the deep sound feedback can also make the system signal too strong, thus burning the amplifier or the speaker (generally burned) The treble head of the speaker) causes damage. Therefore, once the sound feedback system appears in the sound reinforcement system, we must find ways to stop it, otherwise it will endlessly harm.
Whether or not the acoustic feedback can be eliminated is an important indicator to measure the technical level of a sound engineer. Before the emergence of the feedback suppressor, the sounder often uses the equalizer pull point (attenuation feedback frequency) to suppress the acoustic feedback. The reason why the sound reinforcement system produces acoustic feedback is mainly because the sound of some frequencies is too strong. Attenuating these excessive frequencies can solve this problem, but using the equalizer pull-down can produce the following insurmountable deficiencies:
1. The audio level of the sound engineer is extremely high. After the feedback, the sound engineer must judge the feedback frequency and degree in a timely and accurate manner, and immediately attenuate the frequency of the equalizer without any mistake. It is difficult for a rich sound engineer to do it.
2. It has a certain influence on the playback quality. The existing 31-band equalizer has a bandwidth of 1/3 octave, and some of the acoustic feedback needs to be attenuated. The bandwidth is sometimes far less than 1/3 octave. In this case, many useful frequency components are removed. Off, causing irreparable damage to these frequency sounds.
3. It is possible to burn equipment during the adjustment process. It takes a certain time to judge the howling frequency with the human ear. If this time is too long, the device will be damaged due to the strong signal state for a long time. The above problem can be completely solved by using a feedback suppressor, that is, the feedback can be effectively eliminated without affecting the sound quality of the playback, so the superiority is obvious.
The feedback suppressor is a device that automatically feeds the point. When the acoustic feedback occurs, it immediately finds and calculates its frequency and attenuation, and executes the command to suppress the acoustic feedback according to the calculation result. The bandwidth can be set to 1/60 octave, so the phenomenon of affecting other frequencies during the acoustic feedback suppression process is greatly reduced, and the suppression effect is much improved compared to the equalizer. Past feedback suppressors have been technically immature due to earlier development. There are certain problems in function and design, and the effect is not very satisfactory.
Suppresses howling to create a perfect meeting space
Knowing the harm caused by the howling, how to suppress the occurrence of howling? Acoustic feedback causes howling is a technical problem that all sound reinforcement systems encounter and are difficult to solve. The conference system makes the sound feedback howling problem more prominent due to the large number of microphones co-located in one room. At present, there are many techniques for suppressing acoustic feedback, but none of them are absolutely perfect. Usually, a combination of methods is adopted.
First, "speaker automatic switch" and "microphone automatic switch" technology
1. Hand-handed conference system: When speaking to a microphone, the speaker of the same unit is automatically turned off; and when the microphone of the unit has no signal, the speaker of the same unit is automatically turned on. If the microphone button 30s is pressed, the microphone of the unit will also be automatically turned off.
2, automatic mixing type conference system: When speaking to a microphone, the microphone is automatically turned on, automatically shut down when not speaking.
The higher-end conference system adds a built-in adjustable equalizer and howling suppressor. The main control unit of Panasonic's WM series conference system is also modeled after the general mixer. It is equipped with SEND/RETURN (send/return) interface. Users can externally connect audio processing equipment such as parametric equalizer or frequency shifter. Finer regulation of the sound signal to suppress howling and improve sound quality.
Second, variable directional microphone and 4-ECM microphone technology
It has been proved by theory and practice that for different acoustic environments, the use of microphones with different directional characteristics will help to improve the sound gain and suppress the acoustic feedback whistling. General experience, such as podium, stage and other places with better sound conditions should choose a heart-shaped microphone; round table should use a heart-shaped or super-cardioid microphone; especially for the acoustic environment, such as excessive reverberation time or speakers Far from the microphone (such as the leader or a variety of "forums", speakers sitting on the sofa and the microphone placed on the coffee table), you can consider the use of super heart-shaped or even super-directional microphone.
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