Drones are really annoyingly loud. This isn't a bad thing at all.
Airplanes are already heavily restricted in where they can fly.
Airplanes with defective mufflers should be banned too.
Turboprops and jet engines don't really have mufflers per-se. Some aircraft have aftermarket "hush kits", but that's relatively uncommon as well.
My sample size is one, so did I "win" the lottery? I have no particular reason to believe this aircraft is especially noteworthy for its airworthiness or level of care.
I extrapolate, perhaps inappropriately, that the combination of an FAA ban on commercial drones and a testing initiative will mean that only proprietary, patent-protected, and closed-source drones--and their software packages--will ever have access to this potentially interesting and useful market.
And that barrier to entry will make everything more expensive, in the same way that a GPS becomes more expensive when installed in an avionics panel than when it is strapped to the pilot's thigh.
Premature optimization is not optimization at all.
* note - I didn't read your links completely.
That article is from almost two years ago. Use ducted fans, find ways to generate more lift at slower prop speeds.
So that's still louder than a lot of the hobby drones out there today. Having flying chainsaw-level noises everywhere will still be pretty annoying.