To hear, one must first collect sound wave via the outer ear, or pinna. The waves are then channeled down the ear canal to the eardrum. When the sound waves hit the eardrum it causes vibrations to occur, which causes three bones in the middle ear – the malleus, incus, and stapes (hammer, anvil, and stirrup) – to move. The smallest of the three bones, the stapes, fits into the oval window between the middle and inner ear. When the vibrations cause this window to move, the fluid in the inner ear transmits the vibrations into the hearing organ, called the cochlea.
In the inner ear, thousands of microscopic hair cells are bent by the wavelike action of fluid inside the cochlea. The bending of these hairs sends nerve impulses that are passed down the auditory nerve to the hearing center in the brain. The brain center then translates the impulses that we recognize as sound.
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