I heard all of them when I did this the other day, but I think 16 or 17 was pretty quiet to me. I have one air tool at work that has a small leak that makes a whiny sound but nobody I work with can even hear it. It drives me crazy. I always wear large 3m brand ear covers instead of foam ear plugs at work. When I went to concerts when I was younger I always used ear plugs just to cut the volume down to an enjoyable level. I guess it has paid off.