Exercise 1 - Zack, Alex

How The Ear Works


Your ear picks up all the sounds around you and then translates this information into a form your brain can understand. One of the most remarkable things about this process is that it is completely mechanical. Your sense of smell, taste and vision all involve chemical reactions, but your hearing system is based solely on physical movement.

To hear sound, your ear has to do three basic things:

1. Direct the sound waves into the hearing part of the ear
2. Sense the fluctuations in air pressure
3. Translate these fluctuations into an electrical signal that your brain can understand.

The pinna, the outer part of the ear, serves to "catch" the sound waves.
Once the sound waves travel into the ear canal, they vibrate the tympanic membrane, commonly called the eardrum. The eardrum is a thin, cone-shaped piece of skin, about 10 millimeters wide. It is positioned between the ear canal and the middle ear. The eardrum is rigid, and very sensitive. Even the slightest air-pressure fluctuations will move it back and forth.
Before the sound passes in to the inner ear, it must be amplified.
This is the job of the ossicles, a group of tiny bones in the middle ear. The ossicles are actually the smallest bones in your body. They include:
The malleus, commonly called the hammer
The incus, commonly called the anvil
The stapes, commonly called the stirrup

When the eardrum vibrates, it moves the tiny ossicles - from the hammer to the anvil and then to the stirrup. These bones help sound move along into the Cochlea, a small, curled tube in the inner ear. The cochlea is filled with liquid, which is set into motion, like a wave, when the ossicles vibrate. When sound reaches the cochlea, the vibrations (sound) cause the hairs on the cells to move, creating nerve signals that the brain understands as sound.