2002 radio speakers hiss when off

I just noticed, after owning this car for a few months, that with the car off the front radio speakers hiss very softly, all the time. The chime works as it should with the key in the ignition, but otherwise they both hiss, with doors open or shut.
Anyone else had this happen?

Here is the latest update. Tonight I was sitting in the car reading the ops manual, and noticed after the door had been opened and then closed again, the hissing stopped. It's almost like the it was part of the open door chime programming, and the BCM times out after about 15 seconds. In other words, it only does it with either the car running or a door open.
I was just curious if anyone else has noticed this with these cars.

If everyone read the manual, there would be a lot fewer posts on this board!
I have a 2000, and mine hiss just like yours.