Paul_Sengupta wrote:ANR cancels the bass sounds the most, so mostly the exhaust and prop noise, leaving all other higher frequency sounds more clearly audible.
That's certainly been my experience after switching to a noise-cancelling headset. I'd never really noticed the sound of the wheels touching the tarmac on landing - but now I hear them clearly every time (either that or my landings have deteriorated!). Stall warners are still clearly audible too.
The other thing I've noticed is that it's sometimes possible to hear other aircraft engines in the background of their radio transmissions. The first time that happened it was a bit disconcerting (where's that other engine noise coming from?) until I twigged it was coming from the radio!