It is actually a known fact that on many cam designs, in the right position they will reduces string oscillation, and thus noise and get ya couple or three FPS.

If they did not work why do so many bow companies have shrink tubed nocksets near the cam/cams?

It takes alot of experimenting and a chronograph though- some bows will never see a gain, and once in awhile you'll find one that picks up a surprising amount of speed. the old Martin Fury did that- tons of string Oscillation- Picked up 11 FPS using the old rubber "speed demons" about 1.5 inches from each cam lobe.