I saw The Who twice at Hammersmith 73 and Charlton 76 (126 dB broke world record) and they were the loudest shows I'd ever attended, I saw Led Zep at Earls Court 75 third night but it wasn't painfully loud. AC/DC in 81 were louder than Led Zeppelin but weren't that loud. The only band I've seen live who have come close to being as loud as The Who were Rainbow in 76.