[mr48chev]

I remember Wichita from a few years ago when we were down there on the 4th and I some kid with a donked out Caprice bust a brand new rim and tire on a pothole three blocks from the tire store I saw him pull out of with the paper sticker still on the tire.
I still get emails from the Goodyear store there on the other side of town that fixed my tire on the 4th. Hit a show in Park city on the 4th that year.

Back to the original subject I think Joe pretty well hit it. Correct sound deadener, properly placed and well sealed openings. There is a lot of info on the subject on the audiophile forums. They don't like the sheet metal vibration interfering with sound quality on high end systems. The reason you hear some of these cars that the kids who have a big amp big sub and not much for other speakers buzz from the vibration when they go down the road with it cranked up and you hear the metal vibrate as much as the sound.