On a plane, as a passanger, I can't hear my own breath. I can't hear my own breath even in a silent room.
On a plane, there is a continous background noise.
And the microphone recording the noises in the cockpit, are probably not directly at the lungs of both pilots.
I am really wondering, how can the breath of a pilot simply be recorded on the cockpit, if it wasn't designed specifically for that (or it isn't a very high quality recorder placed directly to the body of the pilots)?