I am ASSuming that the sound is a fan for the amp for the stereo as there is no air moving out any of the vents.

The fan is running when the ignition is turned off, but the fan goes off when the key is removed from the ignition.

Just wondering if anyone else has noticed this.

 

The radiator fan runs after shutting off the engine also.

 

Oh, this is much quieter and inside. I'd not be worried about the radiator fan!

:)

I'm just wondering if my hunch is right that it is a fan for the stereo/amp.

 

Yes, the stereo has a little fan on it. The one on my car is much quieter than the one that was in my old Blazer.

 

I've never had a fan in any stock stereo system on any of my Chevys, Buicks or Cadillacs (even an STS!). Or they were just quiet.

I'm cool with it now that I know what it is for sure!!

 

Yup. I hear it in hot weather. It definitely seems to be for the stereo/amp.

 

Cool. I didn't know that.

I noticed it this summer when it was really hot, and was thinking that something had gone wonky with the blower fan from running the A/C.

 

I hear mine (fan running on in the dash after key-off), but I think it shuts off when you open the door.

 

Yeah, I hear mine too. And yes it does shut off with opening the door.
You can hear it real well with the radio off...