This is a significant issue for residents within several km of some
installations and there is
at least one wind farm noise study out of the Netherlands that touches on it.
You might
have some luck searching on 'pylon thump' if you were interested in prior info.
Bill R.
>
> Dear Nature Recordists,
>
> A while back I posted about an un-recordable sound I had heard, a
> mile+ downwind of some of the largest windmills in the world... doing
> the math lead to numbers that did not make much sense, as far as prop
> rates, and the resultant frequencies of any generated waves... and,
> yet, there was a sound, coming from these windmills...
>
> Well, today, I was downwind, maybe a quarter mile, of a single, much
> smaller windmill (not a whole field of giants, with the possibilities
> of harmonics, constructive and destructive interference, and so on)
> and watched the sound being made.
>
> No kidding.
>
> It appears to be an interaction between the blades and the tower. As
> each blade passes in front of the tower, in interferes with the
> windflow. On/off, On/off, what results is a wave of pulses downstream
> from the tower. The blades do not make it, by themselves. The tower,
> by itself, makes no sound. Put the two together, in a steady breeze...
>
> Of course, I did not have my recorder with me. But now I know what
> conditions bring this about. I bet there is some function
> (relationship) of the distance between the blades and the tower, and
> the wavelengths of the resulting sound.
>
> Stay tuned...
>
> Mark
> ~~~~
>
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