I'm hoping it's just a few hangers or some nuts and bolts. I'll either put it up on a lift and get a look at it or put it up on some jack stands...no increase in sound? could be something as simple as a bad/missing rubber hanger.
find a muffler shop. Hope it can be fixed with just some welding or a coupla rubber hangers.
until someone looks under there, you won't know what needs to be done.