I'm not sure what caused mine in either instance. I work in a trophy shop (I'm the graphic artist there, I get to redraw logos when folks bring me really bad versions of theirs, adjust photographs, set up files for glass etching, etc.). But I'm also in the same room with our three laser engravers. Two of them are small and relatively quiet, but the third is a heavier-duty fellow with louder cooling fans. None of these are on ALL DAY, but all of them are on SOME of each day, sometimes two at a time, on rare occasions all three. The first time I got T we had ONE entirely different machine (an extremely quiet one) but the exhaust blower for it was mounted above the ceiling tile (and that was pretty loud). But in spite of no change in my work surroundings at that time, the T still went away that first time. I went for years afterward in the same situation with no T. We even remodeled the room and shunted the exhaust blowers (by now there are two) to the outside of the building entirely. Now the main source of noise is that one larger engraver - it's a large-wattage model and as such needs more cooling, hence more fans - it's almost as loud as the blowers used to be. I work with a few other folks in this same room, one of whom has been there longer than I have (which for me is fifteen years) - no one else has developed T. Just me, sigh....
One morning about three years ago, I woke up and the noise was back in my head. A DIFFERENT noise than what I remembered from before - higher pitched, and accompanied by a clattering rattling noise. That clattering noise comes and goes - which is good because it's the sound that drives me up the wall the most - and four doctors later I think I've heard the gamut of comments. First doctor (general practitioner): "Sorry. This isn't my specialty, I really have NO idea. Let's send you to an ENT". 2nd doctor, ENT #1: "Let's wait a while, it will probably go away on its own". After about eight months and two hearing tests that said my hearing was normal for my age bracket (I'm 54) with only the hearing loss that would be attributable to simply being middle-aged present - nothing out of the ordinary that someone could point to and say "see, right here, this is probably where your T is coming from" - and after being patted on the back by the other doctors and told "it'll go away" I went for ENT #2 and had another hearing test, with the same results - this one said flat-out and rather coldly, "Nothing I can do for you. Sorry." and all but ushered me out of the office, with an over-the-shoulder comment as he walked away of "If it bothers you that much maybe you can try biofeedback". I left that office crying my eyes out. For a while I didn't go anywhere else ... just discouraged. Finally I heard of a TRT program in UPMC and I signed up for that - the doctor there was very kind, very honest, but totally sold on his program (he has T also and evidently the retraining therapy worked for him) - as in, if this doesn't work for you there's nothing else in his arsenal to offer. I paid the $500 to sign up, I got hearing test #4 - same results as the other three - and I bought the $1800 pair of sound generators and started wearing them. Now, the doctor had said that the T would probably be worse for a little while when I started - I had no idea HOW MUCH WORSE. For me, it spiked through the roof, got so bad I was hitting my own head trying to stop this new wall of sound. I couldn't take it - I returned the generators in three weeks. The doc said this TRT program has an 80% success rate - I guess I'm in that 20% for whom the treatment was worse than the disease, so to speak.
That was back in May and I haven't been to a hearing doctor since. I've just been working on adapting my attitude rather than trying to fix the T. I don't know if it's a result of my attempts at attitude adjustment or not, but within the last few months the T seems to be a bit quieter on average; it DOES spike routinely but I seem to be able to handle those spikes a bit better and on the quieter days I can go for good periods of time without fixating on it. I *always*, at some level, know it's there - it just doesn't annoy me as much most times now. The first year I think I got maybe two hours sleep a night because of the T, and was seriously depressed and quite panicky; the family doctor prescribed Elavil, which didn't do a thing as a mood drug but was surprisingly effective as a sleeping pill. I didn't like developing a dependence on a prescription drug to sleep, though, so I switched to over-the-counter Alteril (melatonin/l-tryptophan) which works just as well - indeed, a little better because it sometimes calms the T down at night too, it's often noticeably quieter after I take a couple of those. They do make you quite drowsy, though - that's their function, so it's not like I can take 'em all day to suppress the T
I have a loving, supportive significant other (feels weird to say "boyfriend" when we're in our mid-50s, LOL!!) and I thank God that he's been there for me throughout. He held me while I cried myself out night after night because I couldn't find any peace anywhere, and indeed he helped me "hold it together" simply by letting me lean on him. Not once has he ever said anything condescending or belittled what I felt, and that's been a gift beyond compare.