@bobbyboomer, to help you and others in your search for answers, I took your question to Dr. Zapala, audiologist and Division Chair of Audiology at Mayo Clinic in Florida. This is what he has to add. (Get comfortable. It's a long and comprehensive response.)

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From Dr. Zapala

Bobbyboomer asks a very good question: Can hearing aids cause more hearing loss. The short answer is “no” as long as the hearing aid is fit correctly. If the hearing aid is fit correctly, the computer inside the hearing aid will be programmed to automatically limit the sound level entering your ear so that it is safe and more or less comfortable. This is why audiologists make careful measurements with tools like probe mic systems (where a tiny microphone attached to a noodle like tube is inserted into your ear canal during the hearing aid fitting process). Probe mic systems record the sound level in your ear canal to fine tune the hearing aid program to make sounds as comfortable as possible.

The longer answer is a little complicated, but it is just so amazing what are ears do. I am thankful every day that my own hearing loss is manageable (so far).

There are basically two types of hearing loss: conductive and sensorineural. Conductive hearing loss happens when sound does not get to the cochlea normally. Problems in the ear canal, eardrum, middle ear bones (malleus, incus and stapes) or the temporal bone can cause hearing loss that is often surgically or medically correctable. For these types of hearing loss, once sound enters the inner ear, it is processed normally. So if a wax plug causes a 20 dB hearing loss, an amplifier that increases the intensity of a sound by 20 dB will result in clear normal perception of sound. By analogy, this is like having near or far vision. With the right lenses, functional vision can be more or less restored.

Sensorineural hearing loss is very different. It is analogous to macular degeneration. The inner ear or “cochlea” is a snail shell shaped tunnel that is fluid filled. Snaking through the tunnel, winding from the opening, all the way to the coiled end of the cochlea is a membrane. Think of a nylon stocking inserted all the way to the tip of the snail shell. Inside the nylon stocking is a different type of fluid. Part of the nylon stocking is attached to the bony canal along its length so that it can move. When acoustic energy enters the cochlea, a pressure wave is created that travels along the length of the stocking. The stocking is structured so that different parts of it will move to sounds with different frequencies. High frequency sounds will stimulate the part of the stocking near the middle ear. Low frequency sounds travel all the way to the tip of the coil and stimulate that part of the stocking. This is how the ear begins to create pitch and tone sensations. Soft sounds make the stocking move very little. More intense sounds induce larger movement. This is how loudness begins to be created.

On the surface of the stocking (OKAY, it is called the Scala media) there are several tiny specialized cells, haircells. Some haircells (inner hair cells) have several nerves connected to them that travel to the brain. When the Scala media moves a tiny bit, as in response to a soft sound, only a few of the connected nerves are stimulated. When the Scala media moves a lot, as in response to a loud sound, most of the nerves are stimulated. This is another way sound intensity is coded into loudness sensations.

If there are inner hair cells, there must be outer hair cells. Outer hair cells do something very different. If a sound makes the Scala media move at its tuned frequency, these cells act like springs, changing the way the stocking moves. For soft sounds, the outer hair cells amplify the Scala media movement, so that the inner hair cells get stimulated to very, very soft sounds. When sounds are more intense, they stop adjacent areas of the Scala media from moving so much, improving pitch perception. All of this requires energy. In normal hearing ears, a lot of energy is used to detect soft sounds and develop refined sensations of pitch and loudness.

So when these structures or processes are damaged, hearing loss occurs. But it is very different from conductive hearing loss. Three and sometimes four things happen. First, the ear losses the ability to detect soft sounds in the damaged region (hearing loss). Second, the ear can’t encode loudness the same way. Soft sounds may not be heard, but loud sounds can become unbearably loud. Third, the ability to resolve frequency diminishes. It becomes harder to distinguish between similar sounds –sounds get distorted. And finally, damaged cells and nerves may begin to fire off on their own, causing the sensation of tinnitus. (BTW, tinnitus can be caused by conductive hearing loss as well – through a different process).

Hearing aids have little computers that can be programmed to make soft sounds louder, and loud sounds softer. They can attempt to only amplify sounds coming from a specific direction or only amplify sounds that might be speech. They are really amazing devices. But sadly, they cannot, at this point, overcome all of the distortions that occur with sensorineural hearing loss. There is some good news though…. But first a little math.

If a person has a 40 dB sensorineural hearing loss, they will not like 40 dB of amplification. Loud sounds become too loud in sensorineural hearing loss. So a well programmed hearing aid will try to shoehorn sounds to fit in the hearing range where they will be perceived to be comfortable and speech understanding will be optimal. So maybe 30 dB of amplification to soft sounds for example, 10 dB of amplification for moderately loud sounds, and actually reduce the level of very loud sounds. …And the hearing aid will do this for a multitude of frequencies because in sensorineural hearing loss, pitch and loudness perception changes with frequency. I say “shoehorn sounds” to be comfortable and speech understanding will be optimal, but this is not always possible. Sometimes there is a tradeoff and the audiologist and the person with hearing difficulties will need to decide which is more important. Sensorineural hearing loss is challenging!

So the good news… You don’t really see what you think you see. Hold your thumb up in front of you and look at the far wall. How many thumbs do you see? Answer: 2. Look at your thumb, how many walls do you see? Answer: 2. Over the years, your brain has learned to interpret the two images striking your eyes as a world with depth.

You don’t really hear what your ears hear. 🙂 Your brain learns to interpret the sounds that strike your ear drums into a rich three dimensional world. That is why many people do not recognize that they have hearing loss. The brain adapts – within certain limits. So if you are having trouble adjusting to hearing aids, be patient. To some extent the brain can adapt. When that is not enough, using assistive technologies such as remote microphones and loops can help. Cochlear implants are also always improving and can help in more severe cases of hearing loss.

The really good news is that one day, we will very likely be able to grow new haircells and nerves. …or maybe we will create a technology to replace them. I did not think I would see that in my life time, and there is still a lot of work to do. But I am amazed at what has been accomplished. Keep the faith!