Mk4 helmet passive attenuation
Try asking MoD for the noise measurement reports of each aircraft/environment that were carried out many yonks ago. Depending on the Trainer/Simulator, you should always remember take into account hours there, as many are designed to reproduce aircraft noise.
My advice would be to speak to QinetiQ at Farnborough. They hold all MoD data. 01252 395496. Ask for the Human Acoustics Technical Leader. She's brilliant.