Category: Noise abatement

Mix and Matching Propellers Reduces Noise

It took some outside-the-box thinking by the folks at Aurora, a Boeing-owned company, to arrive at this invention. They asked the question “but Why are drones so loud?” The answer is not so simple: constructive interference. When a propeller spins, it has a noise profile. This noise profile is part spinning motor, part propeller’s interaction with air. This profile has peaks and valleys. Add 3 more propellers with identical noise profiles, and the peaks and […]

A Quieter Propeller: Chasing the Unicorn

This may be old news, but let’s look at the toroidal propeller patent from 2020. It is a valiant attempt to make drones more palatable for the general public. The idea came from the “ring wing” design, an airplane with a wing in the shape of a ring. Tests in WW2 were promising, because this design spreads out the vortices normally concentrated at the tips of regular wings. The inventor of this design (interview here: […]

Amazon Quells Drone Noise with Anti-Noise

Phase cancellation is an interesting acoustic phenomenon. If two identical signals are 180 degrees out of phase, they will completely cancel each other out. With the eventual proliferation of delivery drones, noise will be an issue. As Amazon puts it, “the net effect of the noises generated by the unmanned aerial vehicle may be annoying at best, or deafening at worst.”   Behold: the Silent Drone. Amazon has presented a patent application “directed to actively […]