I have a Proven 6. It is 55m metres from my house and in a severe gale with the wind blowing directly at my house I can't hear it through double glazing. Outside in those sort of wind speeds it roars like a helicopter but the noise is soon lost against the wind noise in your ears. 200 metres away in a severe gale it can occasionally be heard downwind, but only if you are really trying to hear it. In normal winds it occasionally ticks, rattles or squeaks, but normally there is a swooshing sound that I don't find annoying. Having said that, it is making my electricity. If it belonged to some-one else and was within a couple of hundred metres of me I might find the faint background noise of it annoying on a quiet summer's evening.
On the subject of the Iskra turbine noise, I sympathise fully with the problems being experienced. As I said before, I had problems with my Proven initially but these were sorted out eventually. Proven dragged their heels a bit at first but came up with a solution. Getting Trading Standards and the Energy Saving Trust involved in my case helped, so their lack of help in the Iskra case is a disappointment. On paper we have rights as consumers. In the Iskra case it seems that the reality is somewhat different.