I had a hearing test a few months back, and apparently one of the tests for hearing damage uses a headset with a hard plastic foot instead of one of the phones, that they place on the back of your head, hard against the bone. It uses bone conduction, instead of the air conduction for the side with the hard foot, and if you can hear the hard foot better than you could with the speaker, that indicates one type of hearing loss.

So, even with ear protection, you're going to hear the vibration sounds, even if you don't hear the gas driven sounds. You'll get the banging of 12 cylinders and their assorted valves, but you won't necessarily hear the howl of the exhaust.

Now I suddenly wonder if pilots were hearing the firing of nearby rounds, or if they just hear the sonic booms as the rounds went past? I recall something about early investigations into the speed of sound being started by some infantryman wondering why misses cracked twice. Then again, when we're talking about machineguns, how do you tell the difference between the 2nd crack, and the 2nd shot?

Harry Voyager