ok, so this guy is in the UK National Service shooting really loud guns right next to his ear. over the next few decades, his hearing was severely diminished. he got a hearing aid, even.
then, kid goes skiing and, whilst on the ski lift, hears a loud "pop!" and his hearing is back. clear as a bell.
and now for the extremely british response:
"Regaining your hearing because of a change in altitude is very unusual - and the NHS aren't going to be prescribing holidays to the Alps anytime soon!"
no they bloody well aren't!