Former AC/DC frontman Brian Johnson has revealed crystallised fluids which "had been eating away at my ear" accelerated the hearing loss which forced him off the road.
The likeable rocker and car racing enthusiast told American radio station Sirius XM he noticed reduced hearing in his left ear after he forgot to put in earplugs at a New York race eight years ago.
The roar of the engines caused a pop in his ear which led to a bout of tinnitus which cleared up several months later.
He continued to record and perform with AC/DC but Johnson suffered a major setback four months into the Rock or Bust world tour when their Winnipeg concert in September was thunderstruck.
Both he and guitarist Angus Young caught bad colds from the rainstorm which plagued the outdoor gig and immediately caught a flight to their next concert in Vancouver.
"Unfortunately the fluids went up into my sinuses and around my ear," Johnson explained.
His right ear wouldn't "pop" this time and when the band arrived in Australia to kick off the Down Under leg of the world tour, Johnson consulted a Sydney ENT specialist who discovered the "crystals".
"I was getting worried because my right ear is my good ear," Johnson said.
"My left ear is just about totally deaf. And when we got (to Australia), that's when Dr. Chang found out that the fluids had crystallised and had been eating away at my ear.
"So my good ear, I lost - I don't know what percentage but it was enough to make things very difficult. So they worked on me." Johnson said Young and the band's bassist Cliff Williams supported him throughout the treatment.
Dr Chang informed him the hearing loss was permanent.
The singer had to be convinced by his band mates, family and friends to stop touring, with the band finally announcing his departure in April after Johnson had started the second leg of American dates.
Guns N' Roses singer Axl Rose is completing the final American and European dates of the tour.
His Sirius interview puts to rest rumours that AC/DC co-founder Angus Young had unceremoniously kicked the singer out when the full extent of his hearing loss became apparent.
"The boys saw the charts," he said. "I'd been getting checked regularly. And they saw there was a massive dip and if I'd have kept on going, there was a possibility I would never hear again.
"Angus and Cliff just said, 'Johnno, you've got to think of your health.' And everybody else said, 'Brian, your health comes first. You've done a whole year on the road. You've done everything. We want to finish.' And that's what they did. It's simple. What people don't understand is it is what it is." Johnson said he is grateful for the "pretty good run" of 36 years recording and playing with one of the greatest rock bands in the world.
"I had so many good times with the boys," Johnson said. "And I've had such a lucky and great life. And I'm just thankful really that I came out of it in one piece. Now I guess I could rest me socks off." It is not known if AC/DC will continue to tour once they complete this European leg in Dusseldorf on June 15 with several American dates still to be rescheduled.