[samatman]

There's so much white noise outdoors that removing the dominant harmonics that make drones, well, drone,† would make a huge difference in the palatability of being around them.

†The noise quadcopters make has nothing to do with why they're called drones, but is the perfect description nonetheless for the noise they emit

[williamtrask]

If they combined it with audio from the phone they would have a much better chance of isolating noise.