Deresonators

Yeah, on compound bows. You mean a barrel harmonics thing. Looks like an animal call, slides up.& Down the barrel? Yes, they help. Start at end of stock. Slide up to 1/2 way. Maybe further

Some guys use two.

I use them on a couple of my airguns and have seen them take a gun that does

not shoot well and with a little work make a gun shoot very well or a little better .