I recall doing an audiogram on an annual medical. MO scans the printout and says triumphantly, "You're on helicopters, aren't you?". "No". "Then you must be on Hercules". "Yes". Evidently they both wiped out the same frequencies. In the case of the Herc it was caused by doing the walkround under the running ATM. Ear-defenders? No chance, though we were issued with little ear plugs to ram in our lugholes.
To return to the thread, on supply dropping sorties in Borneo the Army insisted we take loaded Stirling SMGs, one per crewmember. These we locked in the fwd loo...not an officer's weapon, don't you know! At the DZ the nav had to lie prone in the bomb aimers compartment below the Hastings Flight Deck, so we gave him all our bullet proof vests to lie on, reasoning that they, and if need be he, would safeguard us wot were up above.