I think some people's ears are more sensitive to others. I'm 18 and believe I have Tinnitus. I have played guitar for years in various bands and ensembles, but I think this year rehearsing in a small room and playing about 5 gigs on small stages (ears real close to hte drum cymbals) we have so far, has hurt my ears. I have a permanent ringing that is more noticeable in my left ear. It annoys me most at night when i'm trying to sleep, but does not realy disturb me from getting to sleep at this point. Tomorrow morning i am getting moulded earplugs made to protect my ears while playing in order to prevent any furhter damage down the track. My other bandmates have no ringing in their ears, even after rehearsal and practice their ears are pretty much fine. I guess this isn't really relevant I just wanted to make people aware that it can be easy for you to do damage to your ears, and most the time it is ir-reverisble so take care!
Chris