Hmm. This question to me at least only matters if you also say what kind of string and whether anything is on the string. then of course arrow weight may come into play. My quietest ever? My Miller Old Tom with a pair of small muskrat silencers on an SBD FF string. All you hear is a whisper of it slip off your fingers and the arrow hit the target. Other quietest bow, a 65" 40# osage hill style self bow w/ a B50 string, no silencers built by a fellow tradganger. Also, like a whisper. Selfbows generally are dang quiet. I had a couple Holm's that were extremely quiet with skinny FF strings.
recently another bow that has impressed me, oddball that it is, is that silly Herter's Itasca I'm trying to sell. It's got a B50 string and a pair of rubber cat whiskers, I loaded up a 780 grain arrow for it and MAN, not shooting super fast, but QUIET, and when that 780 grain arrow hits, the target KNOWS something just happened.