Have you heard a drone? even tiny ones are loud as shit. some guy in my neighborhood flies his drone occasionally and it's super annoying. I can't imagine how annoying these giant drones delivering packages will be.
Yes, I fly them professionally. The sound is related to the size, pitch, and profile of the propellers as well as the speed they are spinning.
The reason the guy down the street is probably loud is he is flying a race drone and hitting very high RPMs with it.
It seems that due to frangibility concerns, Project Wing uses much smaller motors and props now which requires a higher RPM to beat the air into submission.