[trose]

Hopefully Amazon develops some stealthier drones for this program. One commercial drone can sound like an angry swarm of bees on its own. Being anywhere near a distribution center could because maddening if they have hundreds of drones coming and going.

[uberdog]

I'm interested in this as well and did some research on it and apparently most of the noise is generated by the ESCs (the components that control the speed of the rotors) and not the rotor blades themselves.