Geo, what you have is a loose washer in your showerbody.
Have someone check BOTH the hot and cold washers and seats.
After the bibb washer has been replaced use high temperature “Key grease” to lubercate the stems prior to putting them back into service .
This will keep undo wear on the spline when opening and closing this valve.
What it sounds like is water is causing the washer to rattle
(velocity) setting up a hydraulic shock wave, good Luck