They are not able to be heard (at least in a common city setting) above 100ft or so, in my experience. Maybe less. I imagine any drone network would fly at a

They are not able to be heard (at least in a common city setting) above 100ft or so, in my experience. Maybe less. I imagine any drone network would fly at a couple hundred feet for most of the journey, and only be a "nuisance" for the period of time it has to descend straight down to the delivery point.