When singing in howling is a very painful experience, originally well absorbed in the music of the sea, suddenly a crazy microphone barking, then interest also vanished.


Generally speaking, only in the sound reinforcement system has the howling problem, it is in the sound reinforcement system often appears one kind of unusual phenomenon. In the amplifying system when using the microphone to pick up, because regional area and the speaker of the audio playback sound isolation measures may not take the phone, some sound frequencies caused by strong acoustic signal self-excited oscillation, resulting in howling. Howling needs to meet three conditions:
1, microphone and speakers simultaneously used;
2, sound broadcast sound can be transmitted to the microphone through space;
3. The sound energy emitted by the loudspeaker box is large enough and the microphone pick-up sensitivity is high enough.

Howling hazard can not be ignored
Howling once, it will cause the microphone volume not increase the adjustment path, after the whistle is very serious, the live performance will cause adverse effects, when reaching the howling point, microphone sound up will appear after the sound ringing phenomenon of reverberation, destroy the sound quality of the speaker or even lead to power amplifier; and burned because of strong signals.
Because the howling and burning speaker tweeter is not uncommon, because in the howling under the condition of strong signal will appear the amplifier clipping (truncated) distortion caused a large number of high frequency harmonic, treble unit if you can not afford the high frequency signal is so strong, it will cause the voice coil burned; in addition, in the howling state next, if the amplifier output overload, may also be burned.

How to suppress howling?
Howling is an acoustic problem peculiar to the sound reinforcement system, and it can not be completely eliminated. In practice, audio experts summed up a lot of suppressing howling sound system, by taking effective measures and the use of electro acoustic equipment, so as to prevent, reduce and eliminate the howling, the idea is to avoid the sound system while there are three conditions of howling.

1, the sound of the speaker is not easy to transmit to the microphone.
A, microphone away from the speaker.
B, reduce the microphone volume. If the microphone volume is too large, the probability of ringing phenomenon will increase, the volume should be reduced in time to avoid howling. In addition, if you want to hold or wear a microphone through the speaker, but also pay attention to control the volume, otherwise it will be too close to the distance caused serious howling.
C, reasonable use of speaker and microphone pointing characteristics
The microphone and speakers have directivity, if using the microphone location in the radiation area of sound speakers, speaker sound is not easily spread to the microphone; similarly, if the speaker does not pick up the microphone sound in the region, it is difficult to pick up the microphone to the speaker's voice. So, by adjusting the speaker's point of view, the playback area in using the microphone to avoid the speaker, or the speaker sound radiation area and the use of regional microphone overlap, can suppress howling.

2, use electro acoustic equipment to suppress howling
A and frequency shifter. By changing the frequency of the frequency shifter, the howling condition can be destroyed and the howling can be suppressed. But the device has certain limitation, not suitable for use in singing and musical instruments, it is the sound signal to increase 5Hz, used in the language of sound when the effect is very good, because the language in the frequency range between 130 and 350Hz, 5Hz frequency changes will not make people have obvious high tone and feeling; the lower frequency of vocal and instrumental music is about 20Hz, 5Hz listen to the tone change of people has obvious sense of voice tone.
B, equalizer and feedback suppressor
Have a whistle, because the signal of some frequency system is too strong, weaken this part of signal can suppress howling, equalizer and feedback can effectively weaken the feedback frequency gain (pull feed point to suppress howling). The difference is, according to the division of howling sound equalizer need frequency manual pull down the feed point; automatic feedback suppressor can be found and the howling frequency attenuation down, almost will not have any impact on the music, will make the microphone sound becomes good, more suitable for white.
C, pressure limiter
Pressure limiter can automatically change the output signal according to put a lot of input signal intensity (gain), so when the volume to be produced by howling, limiter sound signal intensity exceeds the threshold, so it will not produce screaming. The fly in the ointment is that the use of pressure limiter to suppress the whistle will bring dynamic loss of sound.
3, do a good job room building acoustic design
Room sound dyeing is one of the main causes of howling. The room sound condition is not good, such as room acoustic resonance makes some frequencies in the sound to be strengthened, it will lead to howling. To eliminate room sound dyeing, it is necessary to reduce the occurrence of resonance as much as possible. We have introduced the reduction or elimination of resonance phenomenon, this article is no longer detailed.
In addition, the sound concentration caused by the concave reflection in the room causes the local sound volume in the sound field to be too strong. When the microphone is picked in the region of the sound focus, the whistle will be generated due to the large amount of feedback of the sound energy.
Interior design, should try to avoid the concave reflection or concave made diffuse structure uneven, while using sound-absorbing material and sound-absorbing structure, not only the room for the improvement of frequency response characteristics is good, also can effectively suppress howling.

4, reasonable selection of speakers
The acoustic characteristics such as the directivity and frequency response of the loudspeaker box also affect the whistling. For example, the speakers with large angle are easy to send directly to the microphone, resulting in whistling