Feedback suppressor 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 cannot 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.
In the early days, segmentation equalizer (EQ) was often used as an acoustic feedback suppression device. Since the EQ filter is fixed and immutable, it cannot be accurately positioned to the feedback point. In addition, due to the wide bandwidth of the EQ filter, the depth of the notch is deep, and a lot of sound power will be lost during use. The emergence of feedback suppressors overcomes many of the deficiencies of equalizers as acoustic feedback suppression devices. Compared with the segmented graphic equalizer, it has three major advantages: firstly, it has an automatic function. After setting it, it does not need to be manually adjusted by the sound engineer; secondly, it can automatically search and accurately locate the feedback frequency; the third and most important The advantage is that the feedback suppressor's macro filter does not have to be made deep or wide, it is ten times smaller than the multi-segment EQ filter, which means that the sound engineer can push the system high gain more without guaranteeing howling.
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. However, using the equalizer pull-down can produce the following insurmountable deficiencies: The sound 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 accurately. This is not rich in experience. It is difficult for the sound engineer to do it. The second is to have a certain impact 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. Third, it is possible to burn equipment during the adjustment process.
Strictly speaking, 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.
In addition, the connection method of the feedback suppressor can be roughly divided into the following three types:
First: It is serially connected in series to the sound system like peripheral devices such as equalizers.
Second: use the INS in the mixer channel to insert the plug-in interface, and connect the feedback suppressor separately in the corresponding channel.
Third: use the INS in the mixer group to insert the plug-in interface, and connect the feedback suppressor in the corresponding grouping channel.
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