How Hearing Works

The ear is a surprisingly complex organ responsible for collecting and processing sounds and transmitting them to the brain for interpretation. Many take hearing for granted, but understanding the process is the key to treating hearing loss.

How Is the Ear Structured?

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The ear consists of three sections: the outer ear, middle ear and inner ear. Each plays an important role in hearing.

The outer ear is called the auricle or pinna. It is the external portion visible to others and is responsible for collecting sound waves and funneling them into the ear canal. There, they are amplified and sent to the tympanic membrane (eardrum), causing it to vibrate.

The middle ear consists of the auditory canal and tympanic membrane. When the eardrum vibrates, it stimulates movement of the ossicles, a trio of tiny bones comprised of the malleus (hammer), incus (anvil) and stapes (stirrup). The stapes attaches to the oval window, which connects the middle and inner ears.

The inner ear contains the cochlea, a fluid-filled structure where vibrations transmitted from the eardrum cause hair cells to move. This movement is converted to electrical impulses that traverse the auditory nerve to the brain. There, they are interpreted as sound and the hearing process is complete.

How Does Hearing Loss Occur?

When the outer or middle ear are damaged, conductive hearing loss can occur. This may result from trauma or disease. Damage to the inner ear is known as sensorineural hearing loss, or nerve deafness. This occurs when the hair cells of the cochlea have been damaged, preventing electrical signals from reaching the auditory nerve. Without any information to transmit to the brain, hearing is compromised. Sensorineural hearing loss can be caused by injury, disease, aging, genetics or ototoxic medications. Patients with damage to both the inner ear and outer or middle ear have what is known as mixed hearing loss.

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The outer ear

Ever wondered why an ear is shaped as it is? The shape of your ear ensures that sound waves are captured and directed through the auditory canal into your eardrum.

The middle ear

Three tiny bones and the eardrum make up the middle ear: The malleus, incus and stapes. The stirrup is actually the smallest bone in your body. They work together to amplify sound waves.

The inner ear

Sound processing begins in the inner ear in the fluid filled, snail-shaped cochlea. Sound waves cause the fluid to move and that movement is picked up by the sensory cells that send the electrical impulses to your brain.

The brain

Once impulses are sent to the brain, it processes the data so that we can select what is relevant to the situation and filter what is not.