Ears

Thirty-two individual muscles in each ear allow for a manner of directional hearing:[12] the cat can move each ear independently of the other. Because of this mobility, a cat can move its body in one direction and point its ears in another direction. Most cats have straight ears pointing upward. Unlike dogs, flap-eared breeds are extremely rare. (Scottish Folds are one such exceptional genetic mutation.) When angry or frightened, a cat will lay back its ears, to accompany the growling or hissing sounds it makes. Cats also turn their ears back when they are playing, or to listen to a sound coming from behind them. The angle of a cat's ears is an important clue to their mood.

Source : http://en.wikipedia.org/wiki/Cat#Anatomy_and_morphology