I don't think you can "drown out" noise with more noise. It just gets louder overall. (With the exception of active noise cancelling of course.)

Try whispering when someone is shouting :)

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).

Use the mesh which they already need to have to timesync their onboard systems, and have that modulate the rotors according to their ambient awareness. Profit by having an ubiquitous PA booming down from the heavens above...

While true, you can take advantage of the fact the most people don't perceive 2 sources of identical noise as 'twice as loud'. And given the extensive dynamic range of sound it is not uncommon to drown out sound with noise that's a few orders of magnitude louder.

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.

They aren’t close to identical sounds though. Drones are much higher pitch, and will be clearly distinct.

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.

Yeah... in particular, part of the unworldly annoyance of drones is hearing 4~6 slightly different pitches, all constantly changing, as each prop spins at its own speed to make slight corrections.

There's also a psychological effect. What's louder from ten feet away, hair clippers or a hornet?

Well if a sound is loud enough it's going to drown out everything else just by being much much louder. You can't hear a pin drop when lots of people are talking for instance.

That said I estimate a drone to be much louder than regular traffic, at least inside cities.