aa62,
I was an engine fitter and was issued with a pair of 'ear plugs' in the late 1960s - I say late, meaning that, by then, the damage had already been done by Shacks, Meteors, Hunters, Javelins, Hastings, and one particularly loud chiefy! These ear plugs were presented in a small metal tube with a rubber cap. When I underwent a crew-chief decompression ride at N. Luffenham, I had the aforesaid tube in the left breast pocket of my b/dress jacket; when the pressure in the chamber started to decrease, I suffered a momentary heart attack (or so I thought) as the rubber cap popped off the tube.
The actual ear plugs were next to useless for the job; at Lyneham in the early '70s, I remember there being a reported 73% (IIRC) or so of engine men having some form of hearing damage.
Those glycerine-filled cushions on the ear defenders left a disgusting mess when they failed, too.