I may be mistaken but didn't Vic (500 fps) say that he purchased or was going to purchase a decibel meter for use with his bows. I have not seen him post lately so I honestly do not know.

Then there was a former forum member who actually rigged up his computer to act as a decibel meter for him to conduct tests on but that was many years ago and many messageboards from here.....

The stealth that Matt mentioned always gets rave reviews. Eventually I will get around to trying one but continue to use a variety of other ones as part of my setups.