How the Ear Works
Hearing is the process of changing sound waves in the air into electrical signals that the brain interprets as specific sounds.
Sound waves enter the outer ear and travel through a narrow passageway called the ear canal, which leads to the ear drum. The incoming sound waves cause the ear drum to vibrate. The ear drum sends these vibrations to the three tiny bones in the middle ear called the malleus, incus, and stapes.
The bones in the middle ear amplify, or increase, the sound vibrations and send them to the cochlea in the inner ear. The sound vibrations cause fluid inside the cochlea to ripple, and a traveling wave forms along the basilar membrane.
The wave causes the cilia to move up and down. Cilia near the base of the cochlea detect higher-pitched frequencies, such as a cell phone ringing. Those closest to the center of the cochlea detect lower-pitched frequencies, such as a large dog barking.
As the cilia move up and down, they bump against an overlying membrane and tilt to one side. This is where the electrical signal is created.
The auditory nerve then carries this electrical signal from each ear to the brain, where it is combined and analyzed by timing, volume, and pitch. This information is critical for detecting changes in the environment and separating speech from background noise.