- HOW HEARING
WORKS
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- We don’t
just hear with our ears – we hear with our brain. How does
it work? Find out how simple vibration becomes a birdcall, a
rock lyric or the blast of a jackhammer.
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- While the outer
ear is a great place to display jewelry, it’s specifically
designed to transmit sound. Sound begins as motion. When objects
vibrate, molecules of air are set in motion and transmitted as
sound waves. The outer ear’s bell-like contours guide and
focus these sound waves into the ear canal, where they’re
aided and amplified by its spiraling shape. This natural phenomenon
works so well we copy it to hear even better: a radio announcer
cups his hand around his ear, simultaneously gathering sound
in and blocking background noise out. Once inside the ear canal,
sound waves travel on until they reach the eardrum, the dividing
point between the outer and middle ear.
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- When sound waves
hit the eardrum, they cause it to vibrate, sending the sound
on to the delicate machinery of the middle ear. Here, the body’s
three tiniest bones – commonly referred to as the hammer,
anvil and stirrup – mechanically advance and organize the
sound to further amplify it and facilitate its passage into the
inner ear. The middle ear also contains the eustachian tube,
which equalizes air pressure between the outer and inner ear.
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- The fluid-filled
inner ear is where the action takes place. Here, microscopic
hair cells reside within the spiral-shaped cochlea. These hair
cells are stimulated by the sound wave moving through the fluid
and convert that movement into nerve impulses that are sent to
the brain.
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- From Sound
Waves to Brain Waves
- Our brain interprets
the signals and tells us in turn that the doorbell rang, or that
words are being spoken. Many things help determine just exactly
what it is you hear, but it’s the combination of frequencies
that give different sounds their distinctive qualities. Source
and direction of the sound and loudness are other clues the brain
uses to decipher messages.
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- Hearing loss
occurs when hair cells are damaged or die, a common occurrence
as we age. And hair cells, like brain cells, do not regenerate.
That’s why most hearing loss is irreversible.
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