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U.S. Department of Health and Human Services

Medical Devices

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Animation: Hearing Aid Device

This is an animation showing how the hearing aid works. First, the drawing shows a hearing aid identifying the internal components. The internal components are a microphone, program button, battery, sound processor, and speaker/receiver. A larger drawing shows the hearing aid placed in the ear. The drawing identifies the external components as the on/off button, battery compartment, and volume control.

The animation next shows what you would see if you could view the working ear inside the head. To orient you to the person's head you are viewing, think of the person's head facing you with their right ear on your left. Think of a vertical plane or flat sheet through their head passing through the middle of their right ear toward the middle of their left ear. Now, imagine the front half of the head and face being removed, revealing the inside of the ear. Sound waves enter the external ear, vibrate the flexible surface of the eardrum and the middle ear bones (malleus, incus, and stapes) to convey sound to the oval window of the inner ear or cochlea.

In the animation, sound makes the eardrum wiggle. Since the eardrum is attached to the first of three small bones, the malleus, the malleus moves back and forth. Inside the ear, the malleus connects to the incus, which, in turn, connects to the stapes, which, in turn, connects to the oval window of the cochlea. When the malleus moves back and forth, the incus and stapes move and cause the oval window of the cochlea to move back and forth. The moving oval window sends a pulsating wave to the fluid in the cochlea that stimulates nerves in the cochlea, that, in turn, send hearing impulses to the brain through the auditory nerve.

The animation next shows a similar cutaway drawing enhanced with color to distinguish four regions. It shows sound as a wave in the air outside the head, a vibration in the inner ear bones, a fluid wave inside the cochlea, and a train of impulses in the auditory nerve.

The next series of drawings show the three different types of hearing loss The first drawing explains conductive hearing loss. The animation shows a similar view of the ear, but with lessened transmission of sound from the outer ear to the auditory nerve because of reduced middle ear function. This makes the eardrum and malleus move slower, back and forth. This produces weaker nerve impulses, compared to the normal ear described above.

The second drawing explains sensorineural hearing loss. The animation shows a similar view of the ear, but with lessened transmission of sound from the outer ear to the auditory nerve because of reduced cochlear function. This is shown as the pulsating wave of fluid in the cochlea is not adequately transmitting signals to the auditory nerve because of reduce cochlear function. 

The next drawing explains mixed hearing loss. This is a combination of conductive and sensorineural hearing loss. Again, the animation shows a similar view of the ear, that shows reduced middle ear and cochlear function. The next part of the animation explains that hearing aids may or may not be cured medically.

The next part of the animation shows a similar view of the ear with an In-the-ear hearing aid placed in the ear canal.

The final part of the animation shows the working hearing aid. The animation shows the progression of an external sound wave from the air to the amplifier of the hearing aid in the ear. The sound wave stimulates the malleus, incus, and stapes to send impulses through the cochlea and auditory nerve to the brain.