Actually, there are a plethora of different springs available. I have the 11 lb spring in mine which is 1 down from the full race 45psi capable 12 lb spring. It holds my 17 psi just fine.

The sound is rather unique. It is just a massive rush of air. I can make it sound like it is sneezing. No weird squeaks or whistles. I'll probably be out @ Bennigans on Sunday with it if any one of you are curious as to what it sounds like.