I think I know the buzz your talking about, I'm pretty sure it's the Hard Drive from the radio. I've heard it with the hood open too. Only a couple seconds if that, right?

 

Still no positive answer.

 

Unless it's a totally different sound being talked about, it is not the radio at all. It comes from somthing right on top of the engine, I've had the hood open and if I remember correctly something even moves. I'll get a picture of it when I have the hood open next time.

 

OK, not a picture but this is out of the manual. Im showing you where the sound is coming from. I have no idea what it is or why it does it, but I'm sure someone with more mechanic expierience should know.

 

It's not the radio, I have an aftermarket Sony stereo and I hear the sound.....but have no idea what it is.

 

Mine does it... as long as my key is in the ignition it does this "whirrrrrrr-click" noise every so often. I vaguely remember someone mentioning what it was, but now I can't remember :S

 

There is a sound, about 10 seconds after shutdown, coming from the area noted in the picture. My guess is throttle positioner setting up for the next start.
There is also a sound coming from the area of the radio when a door is opened when the key is off. It sounds like a little electric motor for about 2 seconds. Someone said it doesn't do it if there is a CD in the player. I'll try it tomorrow morning.

 

Maybe the fuel presurizing and getting ready to start?

 

Not to be dumb or anything, and I know it's kind of a WTF is that sound, but if everybody's does it then what's the big deal?

 

If you leave the key in the accessory position, like I do to listen to the radio at work for extended periods of time, I have noticed the same sound repeats every few minutes.