How do we hear?

Advertisement
Advertisement
Eric E. Smouha, MD
Ear, Nose & Throat (Otolaryngology)

Sound is energy carried in the vibration of air molecules. Normally, those vibrations are captured by the ear drum. The ear drum is attached to the three small bones of hearing. The ear drum and the three small bones all vibrate together, and help carry the sound inward, toward the inner ear.

In the inner ear, fine nerve endings capture these vibrations and carry them up to the brain, where they are perceived as sound.

There are three main parts to the ear, including the inner ear, middle ear and outer ear. In order for hearing to occur, there is a sequence of actions that must occur to transform waves of sound in the air into electrical impulses. These impulses are transmitted to the brain by the auditory (hearing) nerve.
 The waves of sound travel from the outer ear into the ear canal, a narrow and delicate tube-like structure. The ear canal goes deep inside the ear to tympanic membrane or eardrum. When the sound waves hit the eardrum vibrations occur. These vibrations are then passed on to the middle ear where there are three minuscule bones: the ossicles, including the malleus, incus, and stapes. These tiny bones magnify the sound and send it to the opening of the inner ear directly into the cochlea, a fluid-filled hearing organ, that’s part of the auditory system.
The multiple waves of sound vibrations cause the fluid in the cochlea to ripple. This rippling effect bends extensions of tiny hair cells in the cochlea and results in the auditory nerve sending electrical impulses to the brain. The brain then translates the electrical impulses into what we know as sound.
Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
Your ear is one of your body's most sensitive organs, as it can hear even the softest of sounds—a fingertip brushing against skin, milk swishing in your mouth. How does it work? Via vibrations and complex circuitry.

In order for you to hear, sound travels down an assembly line of structures—each with its own role in producing sound.

The outer ear contains your eardrum; its role is to convert sound waves into mechanical vibrations that vibrate the three bones attached to the inner ear, which is filled with fluid and nerves.

At that point, a sloshing motion is produced in the inner ear when the fluid is vibrated, moving tiny hair cells (cilia) in the cochlea (a circular structure in your inner ear). The nerves recognize that final step as an electrical connection to send signals to the brain—and that's how we hear sound.

Essentially, your ear is taking sound waves—a form of mechanical energy—and converts it to electrical energy so your brain can understand it. That's right; our ears convert an analog world into a digital one.
YOU: The Owner's Manual, Updated and Expanded Edition: An Insider's Guide to the Body that Will Make You Healthier and Younger

More About this Book

YOU: The Owner's Manual, Updated and Expanded Edition: An Insider's Guide to the Body that Will Make You Healthier and Younger

Between your full-length mirror and high-school biology class, you probably think you know a lot about the human body. While it's true that we live in an age when we're as obsessed with our bodies as...

Continue Learning about Ear, Nose and Throat

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.