The Result of Recruitment
The result of this recruitment causes us two basic problems.
First, the sounds reaching our brains appear to be much louder that normal. This is because the recruited hair cells still function in their original critical bands and also in the adjacent one(s) they have been recruited into.
Remember that when any hair cell in a critical band is stimulated, the whole critical band sends a signal to our brains. So the original critical band sends one unit of sound to our brains, and at the same time, since the same hair cell is now recruited to an adjacent critical band, it stimulates that critical band also. Thus, another unit of sound is sent to our brains. Hence, we perceive the sound as twice as loud as normal.
If our hearing loss is severe, a given hair cell may be recruited into several critical bands at the same time. Thus our ears could be sending, for example, eight units of sound to our brains and we now perceive that sound as eight times louder than normal. You can readily see how sounds can get painfully loud very fast! This is when we complain of our recruitment.
In fact, if you have severe recruitment, when a sound becomes loud enough for you to hear, it is already too loud for you to stand.
The second result of recruitment is "fuzzy" hearing. Since each critical band sends one signal at the frequency of that critical band, when hair cells get recruited into adjacent bands, they stimulate each critical band they are a member of to send their signals also. Consequently, instead of hearing just one frequency for a given syllable of sound, for example, perhaps our brains now receive eight signals at the same time—each one at a different frequency.
The result is that we now often cannot distinguish similar sounding words from each other. They all sound about the same to us. We are not sure if the person said the word "run" or was it "dumb," or "thumb," or "done," or "sun," or? In other words, we have problems with discrimination as well as with volume. If our recruitment is bad, our discrimination scores likely will go way down.
When this happens, basically all we hear is either silence or loud noise with little intelligence in it. Speech, when it is loud enough for us to even hear it, becomes just so much meaningless noise.
This is why many people with severe recruitment cannot successfully wear hearing aids. Their hearing aids make all sounds too loud—so that they hurt. Also, hearing aids cannot correct the results of our poor discrimination. We still "hear" meaningless gibberish.
However, people with lesser recruitment problems will find much help from properly adjusted hearing aids. Most modern hearing aids have some sort of "compression" circuits in them. When the compression is adjusted properly for our ears, these hearing aids can do a remarkable job of compensating for our recruitment problems.
That's interesting. I am sound phobic. I used to have a lot of problems with hearing aids magnifying noises too loudly. In fact the only times I could really cope with hearing aids was when I used to take cannabis a lot. But that also makes me weak and stupid so I eventually chose to think rather then hear and I think I made the right decision although people were putting a lot of pressure on me when I decided to stop wearing hearing aids.
I wonder can wearing powerful hearing aids make the issue worse? I'm asking that because I didn't react quite so badly when I first started wearing hearing aids. It was only when I was wearing really powerful hearing aids that I gradually just couldn't bear noise. Even without them. I went so far as to wear them switched off so the moulds acted as ear plugs.