Also called acoustic regeneration. The mechanical coupling of a portion of the sound waves from the output of an audio amplifying system to a preceding part or input circuit (such as a microphone) in the system. When excessive, acoustic feedback produces a howling sound in the speaker.
"Back in April, you transferred and restored one of my LPs. I never got around to giving you feedback, but today I was prompted to because I just listened to a CD transfer of a friend's LP, a transfer which sounds positively terrible. So, as a point of comparison, I played my CD done by your organization and the difference was astonishing. It ..."