When I served on 30 Sqn I was the designated 'minder' for a university team who had been tasked to investigate noise levels in the cargo compartment of the C130K. They concluded that db levels, frequency range and length of exposure were all contributory factors as was the excessive vibration levels. Their summary was 'it is the equivalent of being in a disco with a pneumatic drill operated nearby and it would not be tolerated in civilian use as a workplace/transport environment even with the use of ear defenders'. Our headsets were described as useless in this context.
You will not be surprise to hear that nothing was done at least not while I was on the 'K'.