I haven't found any suppressor for a Xbow that works for noise. However vibration is hard on limbs, limb pockets, etc. So I dampen the snot out of my Xbow just to help absorb and protect it as much as possible.
How does one go about dampening a Xbow? Mine is noisy on release but thought that was the nature of any Xbow?
String stops are to help with string oscillation and to help cut noise. They do cut down on noise but hard on the string. You can add whiskers to the string. Heavier bolts will help some. Xbows are just noisy.