Try working behind C-141's with engines idling and APU running, or C-130's doing ERO (Engines Running Onload). No amount of earplugs and Mickey Mouse Ears helps. Noise is so great it makes your brain itch. That and screaming motorcycle engines (Formula II and Superbike) is what done my ears in. Probably have 30%+ loss in upper frequencies, ears ring almost all the time, and it's been 9 years since I've done any of that.