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Yes, sorry I should have been more specific. After researching the blades a little further is seems a company called eurocopter did find a way to reduce the no

by nrmn 13y ago

Yes, sorry I should have been more specific. After researching the blades a little further is seems a company called eurocopter did find a way to reduce the noise made by the propellers [1]. Heres a video of the difference between the two blade types [2]. Do you think this would be applicable to the blades at the drone level? [1] http://www.wired.com/autopia/2010/02/eurocopter-moves-one-step-closer-to-whisper-mode/ http://www.wired.com/autopia/2010/02/eurocopter-moves-one-st... [2] http://www.youtube.com/watch?v=dBS1NRsYuF8 http://www.youtube.com/watch?v=dBS1NRsYuF8

Scene_Cast2 13y ago
Helicopter propellers are typically even louder, since the tips are going supersonic (due to the diameter of the propellers). The trademark "chop chop chop" sounds, as far as I know, are caused by sonic booms. The tech you're linking to is about minimizing the source of sound for the sonic boom. Airplane and drone props are entirely subsonic. They make a lot of noise when the pitch is significantly different than the speed that the airplane "should" going at. In other words: if you imagine a propeller cutting through butter, there is a certain distance it would go in one rotation. Propellers are loud when they're going significantly over or under that distance. Also - I'm just a hobbyist, so my explanation may not be correct. This effect is especially noticeable with fixed-pitch propellers used for hovering. For reference, check out these videos. Note that airplanes have 1D variable pitch. [1] http://youtu.be/e8nYZ-fMSHg?t=1m5s http://youtu.be/e8nYZ-fMSHg?t=1m5s - note the sound at 1m12s [2] http://youtu.be/QB6vtE3rIrQ?t=9m15s http://youtu.be/QB6vtE3rIrQ?t=9m15s - note the sounds at 9:25 and 9:53. For more examples, see https://www.youtube.com/results?search_query=propeller+taxiing https://www.youtube.com/results?search_query=propeller+taxii...

by nrmn 13y ago

Scene_Cast2 13y ago

Helicopter propellers are typically even louder, since the tips are going supersonic (due to the diameter of the propellers). The trademark "chop chop chop" sounds, as far as I know, are caused by sonic booms. The tech you're linking to is about minimizing the source of sound for the sonic boom. Airplane and drone props are entirely subsonic. They make a lot of noise when the pitch is significantly different than the speed that the airplane "should" going at. In other words: if you imagine a propeller cutting through butter, there is a certain distance it would go in one rotation. Propellers are loud when they're going significantly over or under that distance. Also - I'm just a hobbyist, so my explanation may not be correct. This effect is especially noticeable with fixed-pitch propellers used for hovering. For reference, check out these videos. Note that airplanes have 1D variable pitch. [1] http://youtu.be/e8nYZ-fMSHg?t=1m5s http://youtu.be/e8nYZ-fMSHg?t=1m5s - note the sound at 1m12s [2] http://youtu.be/QB6vtE3rIrQ?t=9m15s http://youtu.be/QB6vtE3rIrQ?t=9m15s - note the sounds at 9:25 and 9:53. For more examples, see https://www.youtube.com/results?search_query=propeller+taxiing https://www.youtube.com/results?search_query=propeller+taxii...