That's like the days when people used to complain Slade were too loud with a 300watt rig.

Actually, the drummer with Slade became profoundy deaf through the sound ouput - apparently, it's not the actual output of the sound system, it's what you do with it, and Slade were unbelievably loud.

The bass player in a rock'n roll trio I once played in had been their sound set-up man for quite a few of their gigs. He was a hearing/acoustic engineer and used to say: if you wake up in the morning after the previous night's concert, and still have a ringing in your ears - that's permanent hearing damage. He now works as an audiologist in London's ENT hospital.

And, yes, I think the film was early 70s - must check the credits today and confirm.