Turn down your Ipod. Noise-induced hearing loss is being diagnosed at younger and younger ages. It's not just rock musicians, but members of the first Walkman generation are now coming in.
It's not just personal music systems and concerts either. Movie theatres, amusement parks like Disneyland, and restaurants seem to boosting their sound even higher to nerve damaging levels.
If you're worried about your teen, have them check out the Newsweek article. Musicians ear plugs are available at sites like this. Early signs of a problem might include persistent ringing in the ears after loud noises or a thing called a temporary threshold shift, when hearing suddenly seems to get very quiet, but may return to normal.
College Student Hearing Loss
Noise-Induced Hearing Loss
Newsweek: A Little Bit Louder