A thin cone-shaped membrane in the ear canal which separates the external ear (outer ear) from the middle ear.
Sound waves traveling through the ear canal cause the eardrum to vibrate. These vibrations are then passed along to the malleus, incus, stapes (ossicles), and eventually the oval window of the inner ear. The vibration pattern of the eardrum is determined by the frequency of the sound wave.
See also, tympanic membrane