I was running the PA system at a rescue squad awards banquet this past weekend. The event started getting rather boring after the food was all eaten up, and we had to sit and listen to everyone's speeches (NT's for some reason think that captive audiences like to listen to a bunch of rambling) About halfway through the event, I started hearing this subtle howling noise. Naturally, I thought this was feedback from the microphones. I start cutting back levels and turning off unused mic's to no avail. One of the people even said "can someone do something about the sound system". After that, the problem sort of went away for a while without me doing anything, and then it started back up again after several minutes. Because of that, I began to suspect that my system didn't have anything to do with the sound that they where hearing. Then, something down in the audience caught my attention. Several of the teenagers in the junior squad crew were rubbing their fingers on the rims of their stemware glasses...AAAAKKK!! !