The Principle Of Acoustic Feedback In Videoconferencing Camera System

The principle of acoustic feedback in videoconferencing camera system

Video conference camera's acoustic feedback

1. Acoustic feedback (acoustic feedback)

The important factor affecting the sound quality in the sound reinforcement system is acoustic feedback, also known as sound feedback. The suppression of it is an important issue that should be paid attention to when designing and using a sound reinforcement system. When using a sound reinforcement system, you will suddenly hear some trembling or continuous howling. This is due to the high amplification of the sound reinforcement system, and the sound energy radiated from the loudspeaker is fed back to the microphone beyond a certain limit. The whistling phenomenon exists, which can make people unable to hear the sound, and it can make the sound amplification system unable to work normally, and can only return to normal after reducing the amplification of the sound reinforcement system. This situation shows that the acoustic feedback limits the amplification of the system. Use. In fact, the sound reinforcement system was distorted before howling. Does severe sound feedback make the amplification system's amplification impossible to use, the sound reinforcement equipment cannot be used at full capacity, the required sound pressure level cannot be obtained in the audience area, the transmission response is distorted, and it can be felt at certain frequencies. This is similar to the feeling of reverberation in a room, which reduces the language intelligibility of the audience area and the sound quality of the music.

2. Reasons for the production of acoustic feedback

Acoustic feedback is the whistle that is caused by the sound energy being transmitted to the speakers by means of sound propagation. In the critical state where there is no howling, a ringing tone will occur, and it is generally considered that there is an acoustic feedback phenomenon. The causes of acoustic feedback are:

1 The architectural acoustic properties of the site are poor. For example, there is a resonance point.

2 The position of the microphone and speaker is not correct. For example, a microphone is placed in front of the speaker to form a pair of shots with a short distance.

3 Too much boost in the input or output signal in the PA system. For example, the input gain of the mixer, the output gain of the equalizer, the input and output gains of the voltage limiter and the electronic divider, and the like.

4 Excessive boost of some point gain in the mixer tone circuit. For example, mid-frequency gain and low-frequency gain.

5 Excessive boosting of certain frequency points in the system equalizer, such as frequency points in 200 Hz-3 kHz.

6 Excessive increase in the reverberation component of the microphone.

7 Use multiple microphones with different frequency characteristics and different directivity simultaneously, especially omni-directional, high-sensitivity condenser microphones.