
Amazon Patent for Propeller Sounds - jjallen
http://www.uasvision.com/2016/04/04/amazon-drone-patent-for-propeller-warnings/
======
jjallen
Note: this is interesting because the propellers will actually do the talking!

"Accordingly, the controller may determine and cause to implement modulations
of the rotational speed of a propeller, thereby causing the propeller to
produce a series of sounds that are audibly perceptible as “Watch out!”

