http://www.zdnet.com/article/silent-rotor-blades-could-lead-to-true-stealth-helicopters/
According to this, the noise comes from blade encountering vortexes shed off the preceding blade.
__________________
.
.Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster
____________________
.
.Three conspiracy theorists walk into a bar --You can't say that is a coincidence.
|