Anybody have a good guess about the source of a kind of soft, constant, and
slightly high-pitched whirring sound coming from the engine compartment area.
The sound seems to start a few seconds after ignition.  It's not very loud at
all, but it's a little worrisome and sometimes kind of maddening to listen to.
 Is this the sound of an ECU or some other electical component on its last
leg?  Performance doesn't seem impacted in any way and it's been making this
noise for a good while now (about a year).  The main reason I haven't brought
it to my mechanic's attention is that it always seemed such a minor issue
(wishful thinking?) and also my mechanic's a bit older and hard of hearing,
meaning I was pretty sure he would have trouble even hearing the sound.
Actually, I just realized another, possibly more precise way to put this sound
into words; it sounds almost exactly like the sound Bugs Bunny makes just
before saying "What's up, doc?": "EHHH . . . what's up, doc?"  What the heck
would make that sound?

Joe