It’s not just the volume of air but also the speed that it’s moved at. Large slow propellers are quieter and more efficient than small fast propellers. (But les

It’s not just the volume of air but also the speed that it’s moved at. Large slow propellers are quieter and more efficient than small fast propellers. (But less maneuverable.) In the limit, I could see this being done by big, spidery drones with huge props relative to their weight, like a scale model of https://en.wikipedia.org/wiki/AeroVelo_Atlas https://en.wikipedia.org/wiki/AeroVelo_Atlas.