Null,
I 'retired' from spannering in 1965 so I suspect those ear plugs you mention came after my time. One thing I noticed whilst flying on the Hercules was that some the USAF Herc crews wore earplugs inside their headsets. You may recall that the RAF initially issued a form of cotton wool to pax travelling with us. Only later did the disposable ear plugs make an appearance. I wonder how much effect on the complex noise 'soup' of the Hercules these efforts had. I suppose anything is better than nothing.