Feedback

Allow me to help you understand what Feedback is. Also this is an excerpt from my book Essential sound principles.

The ringing noise (commonly described as shrieking, screeching, etc.) that can be heard in sound systems is known as audio feedback. This is caused by a looped signal moving in a continuous loop. 

Acoustic feedback happens when amplified sound from any loudspeaker enters the sound system through an open microphone and is amplified repeatedly. It’s that persistent, ringing tone that ranges from a low rumble to a piercing screech that we’ve all heard. In technical terms, feedback happens when the signal loop’s gain hits “unity” (0dB gain). 

Let’s imagine you position the microphone in front of the speaker. When you tap the microphone, the sound travels through the amplifier, out the speaker, and back into the microphone. This feedback loop is so fast that it develops its frequency, which results in the howling sound. This is an oscillation produced by sound entering the microphone. Putting the microphone too close to the speakers, too far away from the sound source, or just turning the microphone up too loudly, all increase the chances of feedback. 

For more information buy the book Essential Sound Principles by Edison Muhwezi