In the sound of the entire loop, there is a negative feedback structure. The deeper the negative feedback, the better the fidelity. Negative feedback if it is reflected in the circuit, will cause Fei Ming. That is, howling This is the headache for all the operators. Now the best way is to use other equipment, the frequency correction. The most efficient device is the frequency shifter. Is to move the desired frequency, to enlarge. So that there will be no negative feedback in the sound of the embodiment. Usually using an equalizer. Can also be simple and effective control. The equalizer changes the composition of the sound, making the sound fickle. Because the use of equalizer correction, will change the composition of the sound, microphone sound system, have feedback mayor.

Microphone whistling great harm, mainly in the following areas:

1. Self-excited power amplifier will produce a lot of power output, may be beyond the scope of sound reinforcement equipment, burn the power amplifier and sound equipment.

2. When the feedback coefficient is close to 1, the superposition of the delayed sound field and the direct sound will cause the sound field to become narrow in the sound sense than the original sound field due to the comb filtering effect.

3. The delay of the sound field of the loudspeaker will cause the entire system to form a series of delayed echoes, and this echo will exacerbate the comb filter effect, resulting in a significant distortion of the reverberation tail - just distortion.

4. Whistle when the output of the sound pressure is very large, seriously affect the atmosphere of various activities.