Do you have any experience with the kind of multirotor aircraft that would likely be used for short to medium distance package delivery? They are not particularly noisy, and at the distances from humans they would spend most of their time in, they probably would not be audible at all.

I have, I'm the owner of a DJIF450 and I can say they're noisy and I don't reckon they will be delivering to places like NewYork due to restrictions. If your houses are well spaced then I recon your neighbors won't mind.

I assume you're running 9 or 10 inch propellers on the F450. I suspect commercial delivery drones would use much larger props, which should be much quieter. That said, even a 9" quad is not going to be very loud 30+ feet in the air. In a populated area, especially one with cars, the noise wouldn't be audible above the ambience.