I was standing underneath one at a centre on the outskirts of Brighton a year or so back, the Earthship project at Stanmer, where they have one of modest proportions, which is quite a dated model now. It is not one of thise hulking great beasts that major energy projects use, not is it one of the mini ones that B+Q sells, so somewhere in between.
Anyway, my point is, on a day with a pretty stiff breeze, it was making a right old racket! As I recall, the brand of this particular turbine was - ironically enough - WispaJet
(or something like that)
I have been near others since then and noticed no noise in similar conditions of weather, so i guess that technology has moved things on. Thinking about it, that makes perfect sense. I don't suppose that engineers are too concerned with the noise in and of itself, but if the turbine is noisy, it is wasting energy, and they will seek to maximise the latter, thereby reducing the former.
Thanks for the myth busting.
Sven