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A hypothesis about the cause of Tinnitus


The hypothesis


The form of tinnitus that ďsoundsĒ like a low level constantly present sound is a Learned neuronal constant firing in the brain (See chapter 3 to gain a understanding of the meaning of the words in bold )


This neuronal learning is caused by long time exposure to a certain frequency/ies, or by a short time high level exposure to the frequency/ies, or a combination of the two.I consider it possible that mental focus on the tinnitus ďsoundĒ can be self amplifying and contribute further to the long term level of it.


The study


This theory / hypothesis is based on my own case, and purely on my own reasoning about my own case, based on information I have been able to find on the internet and on a TV documentary (Both of German language origin), and finally triggered by a psychology course ( above).My education is bachelor in electronics, and my work has been corresponding.


The case


I first noticed a extremely low level tinnitus possibly about 10 years ago.At that time it was almost never noticeable.Now, at the age of41, it has increased somewhat and is noticeable also in a fairly silent day time environment, and not only in a completely silent night time environment as before.It has evolved very slowly over the period, though it scares me that it seem to have increased in growth (accelerating) recently.




I am not talking about the kind of tinnitus that suddenly comes, and then goes away again (though there may well be a relation).


The arguments


Ifthe sound was coming from the ear, or parts of the ear before or including the ďhairsĒ inside the ďsnail shellĒ (Sorry these are the Norwegian names for it, I donít recall the English words for the inner of the ear), or the neurons in the ear (snail) itself, because itís not very likely that the tinnitus should be exactly the same on both ears, the brain would have detected a difference between the right and left ear, and the sound would have appeared to be coming from a direction (phase / time shift / delay), or only from one side (as can be experienced by comparing to a similar sound from only one side of a ear phone set.This is not the case (in my case), the sound has no direction or location, so the sound must come from a point closer to the brain itself.


My tinnitus is similar to the high frequency sound of a spinning computer hard disc.A sound Iíve been exposed to both at home, and at work, for most of the awake day time. The part at work, for the whole of my career, and the part at home for the last approximately 7 years ††Thus it may seem my brain is now filling in that sound whether itís there or not.My latest home computer have a significant such noise.This may well explain why the sound of tinnitus is different for different people, as I have read several places that it is.


By frequent aerobic exercising, and social dancing, I am exposing my self to a significant amount of high level sound, though not high enough to cause hearing damage (90dB approximately).I have however done this through many years (more than 11 years actually), and during periods to levels above 90dB.Especially when the music is played loud enough to clip / distort, which it seems, most people do not notice (I do however, and so do the modern electronic ear where Iím exercising today).As music also contains the frequencies that my tinnitus exist of, this may have contributed to my case, and possibly still is.


During holidays, we (I) went to some discoís / live bars in the evenings, where there was sound levels much above 90dB. Just after I noticed a noticeable increase in the tinnitus level, but it soon dropped to itís apparently normal level. (This is an indication than one has a hearing damage Iíve read some places). Though, when I look back on these incidents over a period of several years. I come to the subjective conclusion, that these few incidents have also, very slightly, increased the level of my permanent low level tinnitus. But so little each time, that itís not noticeable for a single incident. That is : exposure to high level sounds that most likely causes no effect on people without a hearing defect and without tinnitus, seem to contribute to the long term increase of the level of my tinnitus. This fits well with the understanding I got of neuronal learning at the psychology course (see link above).


One alternative hypothesis would be that this is a part of natural ageing, and not caused by long term / high level exposure too sounds. I could imagine the sensing hairs (sorry, still donít know the proper name for them) in the inner ear could deteriorate with age, but that should then cause silence in the higher frequency ranges (as we know actually happens), and not tinnitus, so I unfortunately can not believe in that as a cause for tinnitus.


Future tests


If Iím right with my hypothesis / theory, then there could be a significant probability that medical ďchemicalsĒ (Sorry, doíno the proper word for it, but they are usually in the form of pills.) used to treat psychological problems, like schizophrenia, that is : medicals used to reduce neuronal activity, could possibly also have an effect on the level of tinnitus. It would be no treatment ! , as the negative side effects would be much worse than the positive (reduced tinnitus), but if it had an effect, it would be one more argument in favour of this theory. If such a finding were positive, treatment of tinnitus could correlate with treatment of traumas.


Other related incidents of relevance


Iíve read that listening exercises can help / ďimproveĒ tinnitus. Which is why I have recorded a CD with a 10Khz to 20Khz sinus sweep over 6 seconds. Iíve not used it much, but when I do, I turn the volume (using ear phones) as low as possible, so I reach the level where it gets difficult to hear the difference between the about 15Khz section of the sweep and my tinnitus. Thus manipulating the sound level, and mentally focusing on hearing the external low level and high frequency sound, I exercise my brain to pay attention towards the external sound, and to ignore the internal tinnitus. But regrettably, I do think thatís what Iím doing. I donít think I un-learn the tinnitus sound on a neuronal level.


About maybe 8 years ago I was working with a angle grinder without using ear protection.After that case I heard a strong sound, not unlike my tinnitus for at least half an hour afterwards, slowly decaying.I have also experienced later that if I go to a disco or bar with live orchestra or other surroundings where you canít talk without shouting 3 cm short of the others ear (much above 90dB), then I hear an increased level of my tinnitus, lasting quite a while afterwards.And when I look back over the years, I conclude that my permanent tinnitus has increased marginally slightly after these episodes.The case with the sound after using the angle grinder, is described several places as a damage to the hearing, which may well be correct, as when I play a 10Khz to 20Khz during 6 seconds sweep sound, on stereo headphones, the sweep becomes un hear able at my left ear before it becomes un hear able a bit after half way through on my right ear.Indicating a reduced hearing in the are above 13/14Khz on my left ear opposed to a stop at 15/16Khz on my right ear, which is normal for my age.However : This incident may also have contributed to a neuronal programming, being the beginning of my permanent tinnitus. And the sound of a spinning angle grinder and a spinning computer hard disc and my tinnitus is not that different.


Iíve accidentally mentioned my tinnitus for a couple of other males in the social dancing community where I go dancing once a weak. I guess they are about 10 years older than me, and they both say they are significantly plagued by tinnitus. They are for sure found of music just like me. That then, gives me a possible future level on the curve indicating my level off tinnitus, that has so far been almost ignorable in everyday life. That curve does not look promising. Not at all.


Open questions and comments (not arguments)


They say tinnitus correlates with blood flow.As there is also a correlation with neuronal activity and blood flow, I donít see that as a argument against my theory. It could be, as the tinnitus seems stronger just after physical activity, like exercising, or car driving, though those activities also involve a exposure to somewhat higher and long lasting levels of sound as well. And itís also stated somewhere that increased ringing in the ďearĒ after exposure to high level sounds, is a indication of a hearing defect / damage. I have not yet focused on noticing if itís increased after pure physical activity without sound exposure.


Iíve sometimes asked my self, if it could be, that for instance a computer hard discs could be making high level (90dB or above) sound in a not hearable frequency range (high frequency), and if that could somehow cause reduced hearing ?. But I have no arguments backing up such an idea, nor have I spent time on it.


Possible treatment


If my theory is correct (see under ďFuture testsĒ above), it would mean I would have to cease exposing myself to the relevant frequencies corresponding to my tinnitus, as much as possible. In my case that would mean ear plugs, not letting through frequencies above 10Khz. I would never dare to walk around with such things visible (and I donít have enough hair to cover them). And a world without music would be like a life without living too me. Because I also exercise when I expose my self to high levels of sound, it means Iím sweating. And the best ear plugs Iíve found so far donít like humidity. Iíve used them for casting my own ones by melted glue. And then cutting them of so they donít extend outside the ear. Iíve never noticed any indication that anybody has noticed them. They have a hole in the centre to let some sound through, but regrettably that causes resonance at certain frequencies, amplifying those frequencies. So itís not a solution. It should be technically possible to make such individually moulded ear plugs with a tiny sound filter in the centre, and not extending visibly out of the ear. The plugs would have to be made maybe 50 couples at a time, because itís impossible not damage them slightly, as you have to use your finger nails to get them out when they are that small, so they have a limited life time. I would be interested in buying such a product / service if anybody offered it.



Finn B. Kjelstrup, SaltrÝd, Norway, May 28. 2004.