The film 'Cone of Silence' is no good for you. I remember it and it only refers to a procedure trainer where some young fireball captain is slagging of an old bloke claiming he was to doddery to find the cone of silence. There is no actual audio of the aid.
Refering to Chugalug2's post I put one in with the Halifax procedure. That, with the chart above, gives you an idea of what it was like. I last flew one in 1961. (not in a Halifax)
