@Diesel I'll expand the hypothesis to incorporate this as well, as its very relevant. Good point.
What I think covers this is inflammation level / healing time of whatever the acoustic shock damaged in the first place. Acoustic shock inflammation seems to have an incredibly long timeline, is very fragile and easily provoked.
I'll give a bit more detail on my own illness because it will help explain my view on it.
I got my first acoustic shock about 3 years ago, for the first 6 months I was in huge pain, every time I thought I was getting better I'd go back to doing slightly louder things and got the pain back all over again until finally I stopped doing anything remotely noisy at all, by the way I was doing pink noise TRT. After 12 months I started to feel much better and did start creeping back to more normal life again, nothing too much, only this time I was getting away with it. As long as I didn't push it for more than a couple of days it was OK. I got careless once or twice and had a couple of small setbacks but it was becoming how I can describe as manageable. At 18 months I was so good I was back to doing pretty everything once again as normal with the only caveat that I was still being careful not to go for too many days without some ear rest, and despite how good it was I still felt the need to be careful . I had about 4 months of normal life back. Then I pushed too far and had a massive setback which I believe may possibly also have been a second acoustic shock. I wasn't doing anything dangerously loud at all but I had been carrying on for about 4 days and it was too much.
I had plotted the first recovery cycle timeline in a spreadsheet and did the same for second recovery. I'm 12 months into the second recovery now and it has been almost identical to the first. The only difference this time is that I'm not doing TRT. I am finding the same pattern of it becoming gradually more and more manageable as the months go by. I'm hoping that by next Feb I'll reach the same 18 month mile stone only this time Ill not be going back to my old life style at all. I'm going to live as quiet life as possible. I sold all my music instruments, music gear, power tools, speakers etc. The main thing I learnt from this is that I now think it very dangerous to ever think I am cured of H. Until a proven scientific model for the underlying cause of H is discovered and then a measurable cure is found I'll have no confidence that I'm ever cured of it. I'll consider myself somewhere within the H spectrum until then.
As for why I believe inflammation is so important in this, I made the graphs below of how I feel at various H stages compared to how I felt with normal hearing and I think the recovery time from any single noise event no matter how loud is lengthened in a H sufferer. I'm talking about the ears natural recovery to any sound I guess, this would not ever be noticeable in a healthy ear as its instantaneous but for a H ear that gets fatigued over hours and days there is that need for extra quiet time. A normal person (us before we got H) for example hears a sound and then goes instantly back to a hypothetical baseline but I think H sufferers return to baseline far slower and so noise has an accumulative effect that kind of bumps up and spends your hearing budget faster than normal.
Another important factor in these graphs is the acoustic shock inflammation baseline. I think there are 2 types of inflammation. There's the inflammation caused by actual damage as a result of the shock, that lets say takes 18 months to really improve, and then there is the subsequent irritations of whatever it is that is inflamed that causes the ups and downs of pain throughout the 18 month period, like a stock market graph on a downward trend. Could this be to do with the way that disconnected raw synapses or maybe altered type II afferents are dealing the signals they receive? If someone was recovering really well, and say they now have reasonably low inflammation and quite a high tolerance for noise again, that is a good thing but I don't think the bumping up effect goes away even though the inflammation does, and if pushed hard enough another huge setback can occur even if it takes a lot more effort. None of this is fact, it just my interpretation of what's happening to me as a sufferer, trying to build up some kind of picture based on the little that is known.
Do synapses reconnect? Do Type II afferents fixed themselves? Possible, because I like so many others did recover very well and get basically back to normal but if in my case the main issue did resolve after the first recovery, it either very soon broke again, or left me susceptible to more of the same while I was only exposed to relatively normal noise, nothing that would generally harm the average person. Maybe 18 months just wasn't long enough first time round for myself.
I think there's a danger that the recovery can eventually appear to be going so well that it takes on the illusion that you are cured but all that's actually happened is that the inflammation has significantly subsided enough to build that LDL threshold back up, that now naturally doesn't get breached nearly so easily as it did when the threshold was far lower. You are easily fooled into thinking you can carry on as normal now, but the underlying broken X factor whatever it is remains broken and very susceptible to subsequent over stimulation from you gaining confidence living an ever noisier life once again. So my best guess is that it is down to inflammation levels of something that is physically broken in the ear. I won't be putting it to the test this time round which is what it really equates to in order to know if I'm cured or not though.
Just a final thing regarding the question of can you consider yourself cured from H? Take 3 people who all suffer an acoustic shock and develop H. 2 of them are regular music loving concert goers and the third is someone who lives alone and has a very quiet life but got unlucky with say an airbag deployment. Assume at 18 months they all feel as good as recovered as they have avoided noise. One music loving concert goer goes back to his old life and has a setback very quickly, he clearly isn't cured and is back at square 1. The second music lover doesn't return to his old life because he's too cautious. His H never returned, is he cured though? How would he know without going back and testing it, he could be cured but maybe not? And finally the one who lives the quiet life goes back to their peaceful life, The H never returned, is he cured? I guess you could say so according to his lifestyle but I doubt he'd want to test it with another airbag deployment. I don't think I could consider myself cured until I could go back to doing all the noisy things that I love doing to test it out but I wouldn't take a chance again until I could be quite sure. I'm sure there are people believe they're cured and Its great for them though.
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