I spent three years working in diesel and steamship engine rooms where, in order to communicate with the fireman or other engineer, our heads had to be almost touching (Hold the sailor jokes). Turbo Diesel - nuff sed; steam turbine roar from the main gearbox and buzz like packs from the turbo feed pump.
We were not issued with ear defenders.
You won't be surprised that I'm not greatly exercised by the loaders with ear defenders having to put up with an APU running for five minutes.