Mark Rober covered the “Zipline” drones which are near silent, unlike almost any other drone you hear. There’s a demo in the video. Done by varying the propell

Mark Rober covered the “Zipline” drones which are near silent, unlike almost any other drone you hear. There’s a demo in the video. Done by varying the propeller design so that the noise is spread out over many frequencies instead of concentrated in the buzzy band. I also remember Apple talking about doing the same in their MacBook pro fans at one point. Varying the blade pitch from blade to blade to do the same. https://youtu.be/DOWDNBu9DkU?si=jW6Iaeobg7j5yAzW https://youtu.be/DOWDNBu9DkU?si=jW6Iaeobg7j5yAzW