Comment by Tor3

When I wear Bose noise-cancelling headphones on airplanes I can hear the female flight attendants much better than when I'm not wearing headphones. The noise-cancelling filters out lower frequencies and constant hum (wind, engines), but not the higher-pitched frequencies (which is why the female voices are easier to hear, and, as you mentioned, crying toddlers). So, when the announcement asks people to remove headphones while they explain the security setup it actually has the opposite effect for me - it makes it more difficult to hear what they're saying if I remove my headphones.

Note that there are different kinds of noise-cancelling headphones. The ones pilots wear are different, and then you have those made for hunters - they are focused at reacting very fast to sounds from shooting.