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PostFighter Pilots and Hearing Protection (Michael Sullivan, USA, 12/15/20 8:25 am)
In response to John E's question, in the 1960s and pretty much up until the Gen 5 aircraft (F-22 and F-35), the jet helmet we wore in the aircraft was like a football helmet with no sound suppressing features around the earphones, as they actually touched your ears.
Then they recessed the earphones a bit into a leather or soft rubber pad so the ear phones wouldn't touch your ear, but it still didn't suppress the sound that much. There always seems to be a constant whining or whirring sound caused by the jet engine and the pressurization system. However, you did get used to the background noise and hardly noticed it until some non-routine radio transmissions would tend to be hard to decipher/understand.
JE comments: I had to do a refresher on the five generations of fighter aircraft. The link below gives a good overview. The 5th generation arrived in 2005 with the introduction of the F-22. They are so "stealthy" that even other Gen-5 fighters cannot see them. Among other fascinating details, we learn that this latest generation of fighter has over 7 million lines of code in its software; another 7 million are written into the ground support network. No wonder they're so expensive!
I hope at least a few of those lines of code are focused on hearing protection.