I have a neighbor who works with Chinese graduate students at University of Colorado. During a conversation she casually mentioned that most of her charges are at least partially deaf. "What?" I commented, to which she told me that when she puts several students into study-groups the volume level of their conversation almost instantly elevates to "outdoor voice" levels as students begin to interact.
When I asked why so many Chinese students had hearing issues, she said, quite matter-of-factly, "Their all partially deaf due to MP3 players..."
Unfortunately there's not much that can be done once someone's hearing has been damaged. Tinnitus (self-generated high frequency noise) caused by trauma from loud sounds is generally not reversible. And while it isn't uncommon for older folks to develop mild tinnitus, but for anyone under 18, tinnitus should not be the issue it has become.
So, what can be done? Frankly, once chronic tinnitus from sonic trauma has begun there's not much you can do, but if it was caused by diet or stress there are some treatment options available.
The simplest way to avoid tinnitus is to avoid excessively loud noise. Good luck with that. As the experiences of the Chinese graduate students indicate, we already have a large number of young people whose hearing is already severely compromised.
If you have anyone under 20 in your immediate vicinity ask them if they make any effort to attenuate their high-volume personal listening. I suspect their answer will be, "What?"
Obviously, that's the wrong answer...
Tell your young'ins about the free smartphone app from Etymotic Research called "Awareness." It monitors volume levels (both external levels and the dB levels generated by a player), could make a major improvement in their lifestyle in later life.