How can the breath of a pilot be recorded? 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)?
One of the channels of the Cockpit Voice Recorder is the microphone on each pilot's headset. This is much closer to the source of the breathing noise than your own ears. The microphone may also not have a wind filter so breathing on it will generate a lot of noise.