Without hearing it , it is difficult, but that sort of sound is often the arrow nock or rear end hitting the bow as it passes. Needs more tuning. Try spraying "dry" deodorant or similar powder stuff on the bow in front of and in back of the rest. Not just the bottom, but also the riser sides. Shoot and see if any marks are left there. That may help rule out or point to something.
Are you certain it is the bow ? Not the string slapping your sleeve or arm guard, or your tab snapping from the laser speed of string release : )
ChuckC