As an anecdatapoint to refute that, I have about 7 or 8 working quadcopters right now. (No, more, at least 9.) All but one of them is totally silent from 100m

As an anecdatapoint to refute that, I have about 7 or 8 working quadcopters right now. (No, more, at least 9.) All but one of them is totally silent from 100m up. Most of them I can't even make out the noise from 50m up. I don't think I'd be personally bothered too much by delivery drones that flew at ~100m and only dropped straight down to my or my neighbours houses to make final delivery. (But I live with a fair bit of aircraft noise already, I'm less than 1km from the main runway at Sydney airport and directly under it's flightpath, so perhaps my level of annoyance isn't typical.) My largest these days isn't exactly a heavy lifter though, 10 inch props capable of lifting a dslr and a reasonably heavy lens on a gimbal - probably 1 - 1.2kg or so of practical payload. I do occasionally play as camera operator of a friend's big octacopter - 16inch props carrying 3 gimballed dslrs (and 3 fixed gopros), so probably 5+kg payload, which is similarly quiet, imperceptible at 100m altitude. (My "noisy" one is one of my smallest, a 4inch prop FPV racing drone that runs 6 cells, it'll do close to 100mph straight up, and practically vanishes within 1 sec if you punch the throttle right open. But it's tiny little props are doing 60+k rpm at full throttle. It's very very annoyingly noisy when flown with vigour. Still hovers fairly quietly though, but its noisier in correcting for gusts than ess extreme 4inch sized quads.)