About two weeks ago my wife called me saying that the car (02 - A6) was making a really loud sound like thunder and static and it was coming from the rear of the car. She though it was the speakers but when she turned off the radio it continued. She said that it continued for about 10 minutes even after she had turned off the car. Of course the issue hasn't come back and I was never able to hear it myself, but I have noticed a noise now that I don't recall hearing in the past. when I turn off the car I can hear kind of a pinging or popping sound (think of an upside coffee can that you push in the bottom and it pops out or an upside down bucket that you tap on with your knuckle) with a bit of static or humming sound and the same time. Now, it's not very loud, but loud enough to notice. I've been able to identify that it's coming from the passenger's side in the trunk wall, not below the trunk floor. It can be heard best standing with the door open and your ear hear or over the rear passenger's side headrest. What in the world is up inside there that would be making this noise?

 

With all the folks on here there isn't an inch of this car that is a mystery, nobody knows what is located in the trunk wall/passenger side? You're not going to make me tear the car apart, are you?

 

My 1st and only thought was expanding/contracting exhaust pieces, all my cars have pinged when cooling down but when you say it's coming from the trunk, then I don't know.

 

In my 99, that's where the subwoofer is. I haven't had that issue, but if it's in the same place on your car, you might want to see if that's where the humming is coming from.

 

thanks guys. I guess I'm going to need to tear in there and find out what's hidden back there.

 

If you have the Bose system, the subwoofer is definitely back there. You can see it if you open the side panel (which also gives you access to the tail light). She may have blown the subwoofer. The other noises...well, now that you're looking for a noise you'll find a noise.