How We Hear

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Hearing is an important function in human communication. Although there are volumes written on hearing and the anatomical and physiological processes of the auditory system, I’d like to give you just a brief description of how we hear.

Sound enters the auditory system through the external ear. The Pinna is made of cartilage and it collects, funnels and even amplifies sound waves into the ear canal. The pinna is more than just a cute place to hang earrings. Its shape aids in localization of sound and boosts high-frequency energy.

Sound waves then travel down the ear canal and hit the eardrum. The ear drum is a tight flap of skin (like the face of a drum) at the end of the ear canal. As the eardrum vibrates back and forth, it transduces the acoustical signal into a mechanical one. The vibrations of the ear drum are then sent through three little bones in the middle ear known as the Maleus, Incus and Stapes. The last bone (Stapes) is like a little piston fitted into a window. The movement of the stapes back and forth displaces a fluid on the other side of the window in the inner ear.

Within the inner ear, the fluid movement causes the deflection of hair cells. You can think of these hair cells as nerve-endings. As the cilica on top of the hair cells deflect, an electrical charge is created inside the cell, transmitting an electrical signal up the auditory nerve to the brainstem, and on to the brain. And, Viola, we perceive the sound.