How the ear hears
The healthy ear can perceive frequencies from 20 Hz to 20,000 Hz. The sound frequencies between 500 Hz and 4000 Hz are those that are most important for speech.
Sound waves are first collected in our outer ear (called the auricle or pinna). Then they travel down our ear canal and strike the eardrum, causing it to vibrate. These vibrations are in turn transmitted to our inner ear by the bones of our middle ear (hammer, anvil, and stirrup). Our inner ear plays changes the vibrations created by the sound waves into electrical impulses, or signals, which can be recognized and decoded by our brain. The inner ear or cochlea is filled with fluid. The movement of bones in middle ear cause this fluid to move. This movement causes the tiny hairs cells lining the cochlea to move back and forth. The movement of these hair cells causes an electrical signal to be sent to the brain. Our brain receives these impulses in its hearing centers and interprets them as a type of sound.
