MacBook Pro :: Random High Pitched Chirps Emanating From Keyboard

I've been getting these high-pitched chirps (beeps? cheeps?) emanating from the upper left quadrant of the keyboard. They seem to happen when I'm doing some heavy photo processing or such. They're not the chirps that have been reported with some MB and MBP on booting up. I've had them now for months, and while I don't think they've got much worse, they've not gone away. I can't seem to make them happen, either.

I've called in to Apple (Applecare runs out in two weeks) to get a case started and will be taking it in to a genius bar to have them run a hardware test. I just wanted to do some due diligence and check in this forum to see if others know about this and what it might be. My suspicion is that it's a logic board issue (though I think this may be something I'd read when it first came up and I was checking on it then). The sound is very electronic, not mechanical, and it has two or three parts to the sound (not one pure beep); it is short, but sometimes happens several times over a few minutes' time.