Even though my Barnett crossbow is not quiet, its one that has never had an arrow miss the aiming point by more than an inch on live animals. That tells me the noise is made up for somewhat by the speed.
Of course I"ve never shot a long show with the crossbow and see no need to either. I just set up correctly and get close shots or none at all.
As to some folks comments about being to mechanical.... lets just say if you bowhunt long enough with anything, anything should become mechanical. If not you are not improving. Its one reason I went to long range rifle shooting, bow hunting, was a given, if they were within my range, there was no question they were dead. Actually got boring after about 30 years of bowhunting...
