He has said recently that he thinks it was caused by his motor racing and not by the music. http://loudwire.com/acdc-brian-johnson-hearing-loss-race-car-driving/
Same here. I went a couple of years between gigs and realised that the post concert ear ringing seemed to be getting worse / longer. Purchased some proper musicians ear plugs and they seem to work really well. If you look around at rock gigs with the older generation attending, you'll be...