Various mentions of Effects of Noise Exposure

"That noise pollution is a byproduct of wind energy generation is now widely accepted. In a landmark case in January, a district judge in Cumbria awarded a couple GBP12,500 in compensation - 20% of the market value of their house in 1997 - because of damage to visual amenity, noise pollution and the "irritating flickering" caused by the sun shining through moving blades. Their house was 550m away."

The wind farm has drawn 262 submissions - 22 in support and 237 opposed. One opponent is the Waiuku Wind Farm Information Society, which says 600 people have endorsed its submission containing a dozen claims, including possible effects on rural views, tourism, health and horse training and breeding. Information society chairwoman Lesley Cotter said it was not opposing wind-power but believed Genesis should have picked a more remote site where the sight and noise of turbines would not affect so many people. She said 7000 people lived in Waiuku 7km away and the district council estimated 500,000 people a year visited nearby Karioitahi Beach.

The noise perceived by those living within a mile or more of a wind farm, and particularly if downwind, is caused by the pressure wave that is generated each time a turbine blade passes the mast. For a single turbine these broad-band pressure fluctuations are not excessively intrusive, but where several turbines operate in proximity the pulses move into and out of phase, creating a doubling, tripling or more in the sound level, depending on how many turbines are grouped together.

Several low-magnitude pulse trains thus cause noise with an unexpectedly strong impulsive character whenever they synchronise. This is inaudible close to each individual turbine but is known to be the cause of considerable distress at greater distances. The effect is much more noticeable at night due to the greater differential between air flow at ground level and hub height and also the greater sound-carrying capability of the cooler night air.