Wow, I'm not the only one! I'm so glad to have come across this thread! I noticed my change with certain sounds at high pitches in June 2010 (and then I had my MAJOR MG outbreak/discover that September). I bet that's what it was. And here I was thinking the band Motorhead was what finally did my hearing in lol (KIDDING!

).
I'm a huuuuuge concert going (heavy metal mainly so you can imagine, quite loud & distorted). I never used to wear earplugs, but then in 2010 (June), I noticed that I just couldn't take certain pitches & the volumes anymore (comfortably). I started to feel freaked out for some reason, and its funny because I felt like I NOTICED the change happen and can pinpoint the time. It didn't seem gradual. I experimented with those cheap foamy earplugs and found that it helped. Now I have a nice pair that helps take away from the distortion (which is what gives you that "ringing" after a concert) and you can still hear the concert loud, but comfortably. It's helped a LOT and I've been doing it ever since. Probably should have done it sooner hehe.
There are a few other things though that I absolutely can NOT stand...like some of those air blow dryers in public bathrooms. The one at my work is really loud, and when the sound/pitch changes because it's blowing on the persons hands, it makes a noise that I just cannot tolerate.