When I was in my late teens and my twenties, I could make a high-pitched screeching sound. It sounded very much like feedback from an amplifier. In college I learned that if I could get someone else to make the lower pitch, kind of a train like woo sound, while I did the high note, it mimicked amplifier feedback almost exactly. I went eeeee, they went woooo. Mike was always the best at that woooo.
There was a party downstairs at Burge Hall, when I lived in the dorms at the University of Iowa, with a live band. Mike and I attended. There was a crowd and we stood close to the band, but not too close. We tried out the feedback noise. The band stopped playing and began to adjust their amps and we thought that was funny.
You'll be happy to know that we were always judicious with our power.