The difference between “recruitment” and tinnitus

I just want to be very clear on the difference between these two phenomena.

They’re both auditory sensory related, but have some significant differences.

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What happened with the “recruitment”?

I got this question from a reader (Candy):

Kim’s post send me here, and I really like your post.  What gets me amazed is that I do have that problem some of the time and I never knew there was a word for it!  😉
Do you have implants now? and, if so, does it helps get rid of recruitment?  If it does, then it would be a good reason for me to get it and stop procrastinating!  😉

Instead of answering Candy directly, I think everybody who has read my original post about the phenomenon called “recruitment”, also deserves to see my response:

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Bad “hear” days and other things

Happy New year everyone!

frustration3 I am a bit frustrated these days, and that frustration has several sources. I feel a bit stagnated and stuck, I can’t track any sound improvement. On the contrary I feel like sliding backwards every time I’m a bit tired. It is like this: when I’m tired, my brain has less energy, less stamina, and the automatic sound processing deteriorates noticeably. I’m having some of those bad “hear” days, these days.

Other reasons for frustration are personal reasons due to me looking forward to move together with my girlfriend, but have to wait for other parties (paper mill stuff) in order to realize it. And the last prime reason for my frustration is that it is absolutely freezing these days (below –4 F / 20 C), and I can’t find all my winters garments as I’m living at two locations simultaneously and both are a mess at the time.

Alway look on the bright side of life!

But on the bright side of life (as Monthy Python likes to sing about :-)  ), chaos and challenges is almost always a good thing. A new order rises from it, bringing new perspectives and a feeling of a fresh start.

I’m not constantly working as hard as I used to, in order to understand speech. (I think I manage that part about not working too hard quite well these days, partly due to the seasonal darkness and feeling of powerlessness.) I’m focused on resting up…

A big life altering decision – a new career

One big important thing that I recently decided upon, was that I’m going to pursue a new career. I’m going to put the IT-career on the sideline, keeping it as a bi-income via my own company, and as a hobby. The IT-knowledge will be useful to me no matter what.

This new career involves me first going back to school for 3 or more years. That fills me with both anticipation and fear. Looking forward to new input, knowledge, making new acquaintances, experiences and fearing the situations where I can’t cope in terms of lectures, meetings etc. Will it, as before, be too much for me to overcome?

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A good analogy of HA, unilateral CI and bilateral CI for hearing people

The following words was observed on Facebook (written by my fellow CI-bloggers) this morning.

A CI blog-friend of mine, Valerie, asked for advice on Facebook:

“Our school will have visitors out next week, how do I explain my cochlear implants and deafness without them treating me differently????

Then another CI blog-friend of mine, “the mad dasher”, Sam Spritzer, offered Valerie a very good answer, and I feel compelled to share this with my readers:

Sam Spritzer at 1:17am December 5

If I were you, I wouldn’t even worry about them treating you differently. You can tell them that CIs are the 21st century version of HAs, only better. And if you have to use an analogy, CIs to HAs are like color tv to b&w tvs. And a bi-lateral CIer is HDTV to standard color tv. Good luck!”

This was the best analogy I have seen to date, in order to explain hearing technology to hearing people. Also he is right in saying not to worry about being treated differently. It’s easy to say, of course, but there’s truth in it. I can vouch for that… Think about something else. Avoid or avert those “worry” thoughts…

So, I just want to rewrite the analogy a little bit:

Imagine hearing aids are like Black&White TV. Then CI is like color TV.

If unilateral CI is like color TV, then bilateral CI is like HDTV.

Explaining the analogy: "Recruitment" of hair cells in cochlea

During my research into my own declining hearing- and health condition, I came across information about a phenomenon regarding hair cells in cochlea called “recruitment”. I strongly suspect “recruitment” is what happens to me. It certainly would explain a lot of the things that happen(ed) to me and my hearing and the fatigue…

(Most of the text that follows is copied from this page at hearinglosshelp.com and edited by myself for the sake of this blog and my readers.)

What is “Recruitment”?

Very simply, “recruitment” is when we perceive sounds as getting too loud too fast. How is it possible to hear too loud when the hearing in fact is vanishing, you may ask… Well, be patient with me and read on…

“Recruitment” is always a by-product of a sensorineural hearing loss. If you do not have a sensorineural hearing loss, you cannot have “recruitment”. In simple layterm this means that this condition only affects those who have a significant loss of hearing caused by haircell-damage in cochlea (mainly).

As a sidenote; there are two other phenomena that often get confused with “recruitment”. These are hyperacusis (super-sensitivity to normal sounds) and phonophobia (fear of normal sounds resulting in super-sensitivity to them). Both hyperacusis and phonophobia can occur whether you have normal hearing or are hard of hearing.

An analogy for understanding how “Recruitment” got its name

Perhaps the easiest way to understand “recruitment” is to make an analogy between the keys on a piano and the hair cells in a cochlea.

The piano keyboard contains a number of white keys while our inner ears contain thousands of “hair cells.” Think of each hair cell as being analogous to a white key on the piano.

The piano keyboard is divided into several octaves. Each octave contains 8 white keys. Similarly, the hair cells in our inner ears are thought to be divided into a number of “critical bands” with each critical band having a given number of hair cells. Each critical band is thus analogous to an octave on the piano.

Just as every key on the piano belongs to one octave or another, so also, each hair cell belongs to a critical band.

The requirements for “Recruitment” 

When you play a chord on the piano—you press two or more keys together but they send one sound signal to your brain. Similarly, when any hair cell in a given critical band is stimulated, that entire critical band sends a signal to our brains which we “hear” as one unit of sound at the frequency that critical band is sensitive to. This is the situation when a person has normal hearing.

However, when we have a sensorineural hearing loss, some of the hair cells die or cease to function. When this happens, each “critical band” no longer has a full complement of hair cells. This would be analogous to a piano with some of the white keys yanked out. The result would be that some octaves wouldn’t have 8 keys any more.

Our brains don’t like this condition at all. They require each critical band to have a full complement of hair cells. Therefore, just as any government agency, when it runs short of personnel, puts on a recruitment drive, so too, our brains do the same thing. But since all the hair cells are already in service, there are no spares to recruit.

Getting to the point – what “Recruitment” means

What our brains do is rather ingenious. They simply recruit some hair cells from adjacent critical bands. (Here is that word: recruit or recruitment.) These hair cells now have to do double duty or worse. They are still members of their original critical band and now are also members of one or more additional critical bands.

With only a relatively few hair cells dead, then adjacent hair cells may just do double duty. However, if many hair cells die any given hair cell may be recruited into several different critical bands, in order to have a full complement of hair cells in each critical band.

 

 

The results of the phenomenon known as “Recruitment” – the conclusion

The results of this “recruitment” gives us two basic problems. (notice the underlined parts!)

  1. 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 brain, 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.

  2. The second result of “recruitment” is “fuzzy” hearing. Since each critical band sends one signal at the frequency of that spesific 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, often mixed with tinnitus 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.

What I hear (or what’s left)

It would be a good idea for me to put down some kind of status as to how my hearing is these days (as a baseline):

Without my hearing aids I can barely hear:

  • My son singing at certain notes at the top of his voice (gives me echo-effect on that frequency until I hear new sounds)
  • A tractor right outside my windows (5 meters away)
  • Only the bass from music

keep-silence With hearing aids in quiet surroundings I hear:

  • Well enough to understand spoken words with the aid of lipreading (better if my head is clear and rested)
  • When really silent: a noisy refrigerator, traffic noise outside the building, an airplane or helicopter in the sky. I get a “white noise” sound from running water.
  • My external hard-drive – the spinning disks vibrate into the wooden table.
  • Other peoples voices in the room, but cannot understand without lipreading.
  • Familiar voices on the mobile for short conversations and messages. I most often have to repeat and ask for confirmation. It’s border-line.
  • Other peoples footsteps in same building, maybe a slamming door.
  • Static noise from electrical FM-devices like my Phonak Smartlink

With hearing aids in a “quiet cafe” surrounding I can hear:

  • Spoken word if not more than 1 meter away, but I have to concentrate really hard
  • Other people speaking, but cannot make out what is said.
  • Music, but only in the form of unrecognised sounds…

 With hearing aids in noisy surroundings I hear:1728

  • All sounds are garbled and mixed in an impossible soup of noise
  • I can extract a voice from 50 cm away if noise isn’t too bad, and I know the subject and the person (if I’m used to lipread whomever, it’s a better chance of understanding)
  • Cars and trucks travelling at high speed close by me
  • Dogs barking loud

When waching a movie with sound directly into my hearing aids I am dependant on captioning. Environmental sounds like running water (splashing), wind blowing, birds chirping etc are lost completely. Spoken words are not understood at all without captioning (dialogue is most often switching and camera angles changing too fast for lip-reading to be effective enough).

Music has lost it’s magic during the last few years. I can sense the rythm, and hear most of the bass and drums. Percussion is completely gone. Perception of vocals depends on type of music and what tone the voice has. Guitar has disappeared slowly last few years, now it’s not “swinging” at all anymore…

I wrote down this, because I want to use it to compare later when I get the CI (my personal baseline).