Roaring is a kind of abnormal phenomenon that conference room sound equipment often appears, the majority of professional sound worker wants to eliminate it, did a lot of work but still impossible will eliminate sound feedback completely.The author believes that the elimination of acoustic feedback should adopt the method of comprehensive prevention and control, start with the research of the occurrence mechanism of acoustic feedback, and explore the method of eliminating acoustic feedback, only in this way can the suppression level of acoustic feedback be gradually improved. Acoustic feedback is the howling phenomenon caused by a part of the sound energy of the speaker to the microphone through sound transmission. In the critical state before howling, there will be vibration ringing (that is, the high frequency end after the sound stops), which is generally considered to be the acoustic feedback phenomenon.After a volume attenuation of 6dB, and defined as the highest available gain, the silent feedback phenomenon occurs.

Conditions for acoustic feedback generation: 

(1) Use the microphone and the speaker at the same time; 

(2) The sound of the speaker box can be transmitted to the microphone through the space; 

(3) The sound energy of the speaker is large enough, and the sound pickup sensitivity of the microphone is high enough. In the sound amplification system, when the microphone is used to pick up the sound, because the speaker pickup area is impossible to isolate the playback area of the speaker, the sound emitted by the speaker is transmitted to the speaker through the space, and the acoustic feedback due to the amplification circuit gain (feedback).Generally speaking, there is only a howling problem in the amplification system, and in the recording and sound system does not have the conditions for howling.If there is only the listening speaker in the recording system, the use area of the microphone and the listening speaker are really isolated. In the movie return system, even if the speaker is occasionally used in the projection room, the projection speaker is far away from the speaker, so acoustic feedback is impossible. 

"Listen to the good voice and gather positive energy!"Guangdong Wanchang Technology Industrial Co., Ltd. is a collection of product research and development, production, sales, engineering projects in one of the modern audio enterprise, its jazz dragon sound for 14 consecutive years won the top ten professional sound expansion system (national) brand title.Adhering to 18 years of industry experience to provide users with quality products and intimate service, the company was awarded the high-tech enterprise unit and municipal technology research and development center certificate by Guangdong Provincial Department of Science and Technology.Market-oriented and project-centered, the company's product business involves professional sound, lighting and stage design, educational equipment, intelligent broadcasting, square dance sound, home theater and other fields.