I was just regurgitating what I was taught really. The tip speed of the two
bladed Bells is no where near the speed of sound and as such tip speed
probably playsvery little towards the cause. If it did, then the faster you
went the louder the slap would be, but the opposite is true. I suspect that
lighter load per blade in conjunction with more blades chopping the wake is
the reason you don't hear it in the more-bladed machines.

BTW: The tail rotor makes the most amount of noise. People say fennestrons
are quieter, I think their sound is more obnoxious , but kinda kewl in
small doses.

Bart

"Justin" wrote in message
oups.com...

B4RT wrote:
The blade slapping noise is caused by the a blade hitting the wake
turbulence from
the blade before it.
Do two rotors cause more, or more concentrated wake turbulence than
multi-blade rotors? Is it still the tip speed of the Huey that makes
the difference?