My Dad's deaf as a post on the right side from having a Browning M1919 fired over his shoulder (drafted, Korea). Now his left side has given out, but that's due more to age. There's nothing that really can be done. Hearing aids don't work with what he has.
I've lost some in certain frequencies due to being a helicopter pilot. While we had hearing protection built into the helmet, as a Maintenance Test Pilot, I still spent my share of time listening to various noises trying to figure out what was wrong. I took steps to prevent hearing loss, but still lost a little. It's documented, but you can only tell if you compare various hearing test results over the years. The actual loss is nothing significant, mainly due to me actively protecting my hearing.
Oddly enough my hearing loss happens to be in the same frequency as my ex-wife's voice[;)]
Ross