There have been alot of replies, but I will offer my 2 cents nonetheless. In the Chinese styles I have practised there are generally 2 different types of noises we would make; HIN; like biting something and HAH like spitting something out They come from the diaphgram not the lungs like others have mentioned. If someone were to press against your diaphgram with two fingers say, each sound will move our diaphgram differently Another is a sharp E! or Yi! and the feeling is compressed and imploding. Different sounds do suit different movements better.