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How the Ear Works

Sound waves travel through the auditory canal and strike the eardrum, causing it to vibrate. The vibrations flow across the three small bones of the middle ear: hammer, anvil, stirrup or stapes. The Stirrup or Stapes passes the vibrations to an area called the "oval window", locked between the middle & inner ear. When the stapes vibrates with the sound waves passing through, fluid in the inner ear carries the vibrations into the canal of a delicate spiral structure called the cochlea. One part of the cochlea has thousands of hair cells which are connected to fibers that make up the auditory nerve. Each hair cell has many microscopic hairs at one end. Movements of the fluid with the aid of an overlaying membrane, bend the tiny hairs. Movement of the hair stimulate the hair cells to generate electrical impulses which are carried up the auditory nerve to the brain.

                

The pinna collects sound and provides natural loudness enhancement of sounds occurring in front of you. Using both ears produces a "stereo" effect and helps you to localize sound (to detect which direction a sound is coming from) and to "focus" on conversations when there is background noise.

                

The middle ear is an air-filled space behind the eardrum. The eustachian tube leads from the middle ear to the back of the throat and serves to equalize the air pressure on both sides of the eardrum, allowing for more efficient sound transmission. When you experience a rapid increase or decrease in air pressure, such as in an airplane, your ear feels plugged because the pressure on each side of the eardrum is unequal. When the eustachian tube opens to equalize the pressure you feel a “pop” and your ear feels normal again.

                

Did you know that your ear is also part of your balance system? The semicircular canals contain special cells that sense the motion and position of your head.

                

The hair cells located at the base of the cochlea respond best to high frequency sound and as you travel further and further along the length of the cochlea, the hair cells are tuned to progressively lower frequency sounds.