Y'all have reminded me of my late father-in-law who was a professional pilot when WW2 broke out. On about December 8, 1941 he enlisted in the Army Air Corps and spent about the first third of the war as an instructor pilot. Once that wound down he moved to the "Ferry Command" where he basically spent all day every day going to the aircraft factories and picking up whatever plane had just been built then flying it to the appropriate port for shipment to Europe. The third third of the war he was stationed in India flying C-54's & C-47's to China supplying the folks who were fighting the Japanese there. He flew nearly 400 round trips India/China/India across "The Hump" as it was called. In fact, he flew the second highest number of trips but as he said "nobody remembers the second man on the moon."
Anyhoo, he spent countless hours in loud, noisy, droning cockpits of multiengine aircraft. As a result, his hearing was shot. I disremember the exact frequency but he knew the exact frequency where his hearing quit. I tested him once by feeding an audio oscillator into an amp/speaker and he predicted the exact frequency where his hearing quit.
Thanks for the memories folks.