Below is a link to a recording of my pool pump's obnoxious noise:
(not sure the link works, but the address is correct)
It's been doing this for quite some time now, but I'm finally getting around to doing something about it It only makes this sound when the pump motor is cold. So, all winter long, it would squeal when it first turned on, then after 5-15 minutes would quiet down and work just fine. I just put the sound together with temperature about a week ago, when I noticed that it wasn't making the noise since the days have warmed up. You can see in the video that I put a garbage bag full of ice on the pump before starting it, just to be sure it would squeal on command for the camera.
We have a Fidelity home warranty (I know they're practically useless, but it was included with the house... ) which covers our pool equipment, so they've sent out a pool service to look at it. Of course I can't produce the noise on command, so I showed their tech this video. His first impression was a perhaps a loose impeller, but said he'd never heard a sound like that before. My thought is: if it were impeller-related, it would constantly make the noise regardless of outside temperature. My gut feeling is bad bearings, which don't squeal when they're warm.
What sayeth the great Oracle at TFP? I may send them (edit: the service guys) a link to this page if you have some ideas.