Silence of the drones: how to hush the humming

摘要

Drones tend to live up to their name, emitting a low buzz that may be a problem if fleets of delivery drones start operating in urban airspace. But a team from NASA has now developed a way to silence that annoying noise. The CL-10 is the latest in a series of prototypes from NASA's Langley Research Center in Hampton, Virginia. It is made from carbon fibre and has a wingspan of 3 metres. But its most unusual feature is the large number of engines, with eight on the wings and another two on the tail. One aim of this is to generate efficient electric propulsion, but the project also solves the problem of aircraft noise: several small motors are quieter than a few large ones. The GL-10 uses Leading Edge Asynchronous Propeller (LEAP) technology, which prevents the sound from the propellers combining into one loud noise or harmonic.