Do you grunt or otherwise make noise while hitting? Do you think it helps you? Do you mind when your opponent does it? I never make noise in practice or when cruising in a match. However when playing a physical point in a close match I typically go to a Djokovic style grunt. Also I often punctuate winners with a prolonged "EEEEEEEEEEEHHHHHH!", a quick fist pump and a stare at my opponent. I don't think this helps or hinders my game in any way. It is just a natural thing I do when I am really zoned in during a match. I don't mind my opponents making noise in the least. In fact, I find female grunters rather attractive;-).