http://www.exhaustsoundclips.com/gm.html This site is attempting to give sound examples of different exhausts. The recordings are a bit rough, but it gives you an idea, I guess.
This info is from an Impala SS forum:
"Glass packs give nicer throaty sound than your stock exhaust. Depending on which way you install it will determine your sound. If you install it with the baffle popouts facing the front of the truck you get the pop and crack sound at high RPMs with them facing the back of your truck you'll still get the nice rumble without the popping."
Shorter = louder, more high end noise
Longer = more low end rumble
I have stock manifolds and dual glasspacks that are about 3' long. It doesn't sound too loud to me. It has a decent rumble, and gets louder at high rpm's.
