Originally Posted by
KqQNr
There's nothing "magic" about the rotors. I've been very near an H-53E on takeoff and "heard" it make almost no sound, yet on other days during rotor engagement one would have a difficult time speaking to a person right next to them. The effect of relative wind on the acoustic signature is far more likely the factor in rotor noise. Also, at least when X2 was flying, the -76 was generally positioned closer to the TM van than the test article (to the best of my recollection).
A 53E making no sound? That I've never seen! Or heard I should say.
When they flew the X2 in Elmira, you cannot say the S76 was closer to the X2 trailer. I was there!