All sound is just a series of vibrations in the
air. That's why there's no such thing as sound in
outer space (no air), and that's why sound travels
faster through solids or liquids (there's more
stuff there to vibrate).
Our outer ears,
the part you can see, collect and focus those
vibrations. In the middle ear, the eardrum is a
tight membrane that moves with those vibrations.
The eardrum is connected to three little bones
called the malleus, the incus, and the stapes.
They move as the eardrum moves,transmitting the
vibrations to a fluid-filled chamber in the inner
ear. As the inner ear fluid vibrates, little hairs
called cilia move in the current.
Each hair or
cilium is connected to a nerve that goes to the
part of the brain devoted to hearing. Our brains
translate the nerve impulses into what we perceive
We can detect the direction of
the sound source if the sound arrives at different
ears at slightly different times. We perceive
loudness and pitch in sounds based on
characteristics of the vibrations. "Bigger"
vibrations,or sound waves with greater amplitude,
are perceived as louder sounds.
vibrations, or sound waves that occur with greater
frequency, are perceived as higher in pitch.
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