They are actually pretty quiet, the newer SS are much more so then the older al. body units. The do have a lifespan if your run them hard, Im an rpm freak and much over 7k alot seems to destroy them inside, then they sound like a straight through race muffler.

On my one ride with a ive two cars with them, the 2.5 system is loads easier on the ear then the 3 inch ones.

I can pm you a vid if you like.