Who went deaf in ACDC?

I'm curious, can you shed some light on the question, "Who went deaf in ACDC?" I understand that ACDC is a legendary rock band with a long and storied history, but I'm not aware of any member who has gone deaf. Was this a temporary condition or a permanent one? And if so, how did it happen? Did it affect their music-making abilities or the band's dynamic in any way? I'm eager to learn more about this aspect of their story.