Suppression method of acoustic feedback

Acoustic feedback is a common problem in sound systems, and here are some effective ways to suppress it:

First, equipment and technology

Adjust the gain structure reasonably

Input gain: Make sure that the gain of the input device (such as the microphone) is set reasonably and does not go too high. It should be adjusted according to the output level of the sound source, so that the input signal level is in the appropriate range, and the signal is prevented from being overloaded at the initial stage and causing acoustic feedback.

Preamplifier gain: The gain of the preamplifier should also be moderately controlled. While satisfying the needs of signal amplification, it prevents the signal from approaching saturation due to overamplification, thereby reducing the possibility of acoustic feedback.

Power Amplifier Gain: The gain of the power amplifier should match the sensitivity and load impedance of the speaker. Too high will cause too much output power, which can easily cause acoustic feedback, so it is necessary to adjust it accurately according to the characteristics of the speaker.

Using the EQ

Notch filter: The notch filter is set by the equalizer to attenuate the frequency band where acoustic feedback is most likely to occur (usually around 2 - 5 kHz, which is the range where the human ear is most sensitive to sound and prone to whistling). The frequency, bandwidth, and depth of the notch can be manually adjusted to precisely eliminate the specific frequency components that produce acoustic feedback.

Graphic Equalizer: Utilize a graphic equalizer to make overall adjustments to the spectrum of an audio signal. Reducing the gain in those frequency bands that are prone to triggering acoustic feedback, while increasing the relatively stable frequency bands to improve the overall balance of sound and reduce the risk of acoustic feedback.

Compressor is used

Limit Signal Amplitude: A limiter can limit the amplitude of an audio signal. When the input signal reaches a certain threshold, the limiter compresses the dynamic range of the signal to prevent acoustic feedback due to excessive signal. It can set parameters such as threshold, compression ratio, attack time, and release time to achieve precise control of the signal.

Protection system: In a sound system, a limiter acts as a protective device to avoid acoustic feedback caused by momentary signal overloads, as well as to protect other devices such as speakers from excessive signal shocks.

Second, the speaker and microphone layout

Arrange the speakers reasonably

Avoid sound reflection: The speaker should be positioned in such a way that the sound is not reflected directly into the microphone. For example, do not place the speaker directly in front of or above the wall, and try to keep the sound of the speaker away from the microphone to reduce the possibility of reflected sound entering the microphone and causing acoustic feedback.

Adjust the speaker angle: Adjust the pointing angle of the speaker according to the shape and size of the room. The main beam of the speaker can be directed at the listener area, rather than in the direction in which the microphone may be placed, reducing the probability of acoustic feedback.

Optimize microphone position

Stay away from the speaker: Keeping enough distance between the microphone and the speaker is the most basic way to prevent acoustic feedback. In general, the farther away you are, the less likely it is that the reflected sound will reach the microphone and be amplified.

Adjust microphone pointing: Point the microphone away from the speaker to avoid directly receiving the sound from the speaker. If possible, place the microphone near a sound source (such as the speaker) and in the direction of the sound source to reduce reception of ambient sounds, including speaker sounds.

3. Environmental improvement

Sound-absorbing treatment

Increase sound-absorbing materials: appropriately increase sound-absorbing materials in the room, such as sound-absorbing panels, sound-absorbing cotton, etc. These materials absorb excess reflected sound, reducing the reverberation time in the room and thus reducing the likelihood of acoustic feedback. Especially in the vicinity of speakers and microphones, sound absorption measures can be added in a targeted manner.

Optimize the acoustic structure of the room: Reasonably design the shape, size and decoration materials of the room to improve the acoustic environment of the room. For example, avoid having too many parallel walls in the room, as they tend to generate standing waves, which can lead to enhanced sound reflections and acoustic feedback.

Quarantine measures

Use a sound enclosure: For some devices that are prone to acoustic feedback, such as microphones or small speakers, you can use a sound enclosure for isolation. The acoustic enclosure effectively blocks the entry of outside sound into the equipment, and also prevents the sound emitted by the equipment from leaking into the surrounding environment and causing acoustic feedback.

Set up noise barriers: Set up noise barriers between the speaker and the microphone, such as screens, sound curtains, etc. These barriers block the direct path of sound propagation, reducing the chance of reflected sound entering the microphone.