So noice-induced tinnitus can't really be fixed once once the damage is there? is it just the brain who starts ignoring the signals from the damaged hairs, or can hair cells in our inner ear actually be healed like a broken leg after a while?
I'm not a doctor, so everything I can offer has been collated from what I have found. Some of it empirical, other parts from clinical studies and medical resources. I have tried to employ some scientific rigor to it, but it is not gospel (funny expression when you think about it).
Hearing cells can be damaged or destroyed. As an example, abuse from music at a gig that is too loud can result in damage and given time, a break from the source of the noise and the right nutrients being delivered to the ear via the capillaries, they can repair. The last part of the sentence is important as lack of blood flow to the inner ear will also destroy hearing over time.
Long term, or serious repeated abuse, without a break, will eventually destroy them as they do not have time to recover and they will die. In this case, with current medical offerings, they cannot be replaced or repaired. As such, this means that this particular hair cell, responsible for part of your hearing is dead and no longer responds to external stimuli - this is not the same as tinnitus though. N.B. That is not to say that research won't catch up.
I have done research work for medical companies in the past (admittedly, surgical, rather than pharmaceutical, but there are analogies in terms of level of testing before release) and those I was involved with over 5 years ago are only now becoming available.
A lot of individuals are seemingly outraged that little is being done to cure hearing loss and tinnitus, but it isn't for a want of trying. There are tens of millions of people globally that have either hearing loss, tinnitus or both and more importantly for drugs companies, the financial means to pay pretty substantial amounts of money to "fix" it. If someone told me tomorrow that my tinnitus would be gone for life but it would cost £1000+ a year for a seemingly simple drug, I would find the money and I suspect many other people on this forum would as well. For a pharmaceutical company, it would be a gold mine. I suspect the annual revenues would be in the trillions.
Auris Medical are just one company working on a fix for this at the moment, but it isn't yet ready and I suspect the recent failures of the Bial drug trial in France could slow down some more experimental drugs from being released, but who knows, it could be appearing within the next year or two.
As far as is tinnitus is concerned though, there is nothing to say that tinnitus won't go on its own. It sounds odd, but the brain has the capacity to just forget that it was tuning into these damaged signals and ignore them completely. I understand that it does happen to some people, but I could not offer any meaningful data as to how often this occurs.