About one year ago I heard that the usually quiet exhaust noise
suddenly had a raspy edge to it. I took the car to my mechanic and he
replaced the muffler at the back of the exhaust system. The exhaust
noise returned to normal (smooth and quiet).

Now I am hearing a very similar sound, but this time from further
toward the front of the car. My mechanic took a close look, up on a
lift and on the ground, but can't find any leaks or holes anywhere.
Does anyone have any ideas about this? My mechanic says I'm not
hurting anything by driving the car like this (he claims he can't hear
anything unusual) but I'd like to get things back to normal again.

Andy