An audible howl or squeal, produced when a portion of a speaker’s output is picked up by a nearby microphone and fed back to the speaker.
"Thanks for the first class work! I appreciated the ability to track my order and the email contacts you provided during the process. I am enjoying the CD right now. It has unlocked some of my most favorite music that I thought would lost to me forever. I could not find a digital version of this music on the internet. This has worked out great ..."