Noise levels in cities are already unhealthy. Adding thousands of small rotors is madness.
Another mitigation could be to specify allowed jump points (for example on big street crossings where the noise from cars would drown the drones' noise anyway).
If the difference is big enough it's like adding 0.01 to 10. You'd need a lot of drones to influence the total noise level noticeably.
From my experience (Fimi 8 SE ~ 300g drone) the drone is annoyingly loud at < 5meters, and becomes practicaly silent at >50 meters (at least I don't hear it anymore).
Though I reckon it's more likely that the constant noise of drones will drown out the traffic noise than the other way around. Not just because it's constant but also because it's LOUD.
It’s like when a car honks or someone whistles on the highway. There is a lot of noise, but the higher pitches are distinct.
That said I estimate a drone to be much louder than regular traffic, at least inside cities.
I'd imagine there's some overlap of "people who race cars" and "people with aftermarket exhausts."
Now imagine that instead of returning something back to a central warehouse, Amazon could have the next customer pick it up or ship it nearby.
Hopefully boxes would not be needed for most of this, too. And any online store(s) could do this.
But I would also love if they could drone the package over to my roof if I wanted to.
It's also something only the fitter half of the population can realistically do.