You've probably witnessed Max's uncanny ability to rotate his ears about his head like little satellites. Maybe you called his name and he turned his ears towards you, without bothering to get up. A cat uses a bank of muscles to rotate his ears to support his fabulous hearing.
Max's ears are made up of three main parts – the external, middle and inner ears. The external ear, or pinna, is the part he can move around with ease. It works like a funnel, moving sound down towards the middle and inner ear. Because of his large, rotating ears, he can pinpoint the exact location of a sound from up to 3 feet away. This is helpful when he hears the high-pitched squeak of a tasty mouse.
Max can rotate his ears a full 180 degrees each, giving him 360-degree surround sound of his environment. He has 32 muscles in his ear that he uses to rotate it around in the direction of an interesting noise. He can rotate his ears independently of each other, and even if he seems to be ignoring you, he probably is keeping an ear on you.
His hearing is incredibly sensitive. He can detect a change in pitch as small as one-tenth of a tone. Cats can hear much higher pitches than you, with his top range being around 65 kHz, compared to a human's at around 20 kHz. His lower pitch range is about the same as yours. Since most of his prey – rodents, birds, or small reptiles – make high-pitched sounds, his preference for these higher-pitched sounds gives him an advantage when he's on the prowl.
Max's rotating ears serve not only to allow him to pick up sounds from all around, but they will give you a hint as to what's going on in his head. When chill and happy, they'll be relaxed and slightly at an angle, and pointed forward. Perked straight-up on top of his head means he's very interested and listening intently. When he's nervous or getting agitated, you'll see his ears begin to quiver. Ears flat against his head means he is angry and ready for a fight. Keeping his ears back will protect them from wayward claws in a cat fight. If he's always quivering his ears or keeping them pinned back, it could be signs of a medical issue. Always consult with a qualified veterinarian about the health and welfare of your pet.