Originally Posted by CRiZO

An exhaust will also change over time too.

I installed a ton of sound deadening in my hatch (for the subwoofer, not exhaust) and a side effect was my exhaust is MUCH more quiet inside the car now.

The only thing separating the driver from the exhaust tips is the plastic bumper cover, the carpet, and literally a panel of sheet metal. If you bang on it, it'll sound like banging on an empty 60 gallon drum. I put a few layers of butyl mat back there, and 80mil closed cell foam. Cut down on road noise some too.