1.5 kilometers Dr. Chris Hanning (UK) - Cape Cod Commission

Cause of Aerodynamic Modulation“Amplitude modulation of the aerodynamic noise at blade passingfrequency must be due to differences in the environments experienced bya turbine blade as the rotor turns…From rotational symmetry, the onlydifferences in a blade’s environment as it sweeps round are due to (a) thedirection of gravity, (b) the presence of the support tower and (c) the windvelocity profile across the rotor swept area.”