I don't know about that, but I know a guy at a nearby store who is almost deaf, and he says it's because he was in Air Force [doing some specific work] for a bit too long. Loud noises from engines that are as powered as we can make them, and there is only so much protection that is even possible, short of a spacesuit.
Oh yeah you get up close to a jet engine running and the sound will go right thru your head & body whether you have ear phones on or not.