Good advice. I have been experiencing the same things you mentioned the past year or so myself. In loud situations, the sound isn't clear, almost sounds muffled to an extent. And occasionally I will get that high-pitched sound you were talking about, sometimes for no reason at all.

I can probably attibute it to quite a few concerts and wearing headphones a LOT. Headphones are really bad for your ears as well, you don't realize how loud it really is but its pretty bad. Be careful out there.