The Nature of Hearing Loss and the Fundamentals of Proper Amplification (Part III)

In Parts I and II of this series, we discussed the symptoms of sensorineural hearing loss and the reasons behind those symptoms.  For Part III, we’ll take a look at why these symptoms are associated with sensorineural hearing loss – also known as “nerve deafness”, which you will soon see, is a bit of a misnomer.

Our ears have three parts:  the Outer, the Middle, and the Inner.  Sensorineural hearing loss, the most common type of hearing loss in adults, is caused by pathologies in the inner ear.  The inner ear is shaped very similar to a snail shell, wound in a circle.  Inside the “shell” is a membrane that runs the length of the inner ear, or cochlea.  On this membrane are thousands upon thousands of microscopic sensory cells, sometimes nicknamed “hair cells” due to the tiny cilia perched on top of them.

Any particular point on the membrane inside the cochlea is tuned to a particular pitch. When a sound enters the Inner ear after passing through the Outer and Middle ears, it vibrates the membrane, which in turn stimulates the sensory or hair cells [at right, click to enlarge].  When these cells are stimulated, they convert the acoustic signal into an electrical signal, which travels up the auditory nerve fibers they are attached to, all the way to the brainstem and auditory cortex in the brain.

It is these loss of sensory cells in the inner ear that are the greatest contributor to sensorineural hearing loss (for this reason, "nerve deafness" is a very misunderstood term) and the cells nestled on the portion of the membrane tuned to higher pitches are the first to go.

To conclude this series, Part IV will cover the basics of proper amplification because contrary to what you may have been told, hearing aids can and do help patients with "nerve deafness".  As a matter of fact, proper amplification benefits millions of people every day.

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The preceding was part of A four part series at Auris Repletus entitled, "The Nature of Hearing Loss and the Fundamentals of Proper Amplification"

- Part I
- Part II
- Part III
- Part IV