with the muffler it is not much louder that stock. Hardly even noticeable. If you remove the cat it gets a bit louder, if you remove the muffler it gets decently loud. With no tailpipe, you can scare pedestrians.
I have the 3 inch cat back exhaust no muffler on my truck from RPM and it sounds really nice, not to loud. I have had no law enforcement problems from it yet. easy install. great quality of work.