I did a measurement today at 1000 m downwind of the nearest turbine at a Wind farm site in the Midlands. Interesting to see that the noise levels where in the order of 38dB,LA90.  I did not have access to the windspeed at hub height, but local winds nearby was measured at 0.25 m/s and there was no audible when generation noise foliage. In addition to this there was no evidence of any modulating are elevated third octave bands.