Alec Salt, a researcher at the Washington University School of Medicine who has discovered interesting things about the inner ear's response to low-frequency noise, notes at Wind Concerns Ontario that reports finding no significant ill effects of wind turbines on health or property values all appear to use an cutoff of 5 or 10 kilometers or 5 miles.
It is obvious that with such a cutoff, you are guaranteed to dilute any effect by including a vastly larger number of people and property at greater distances from the wind turbines. Salt puts some hypothetical numbers to that fact, which I here adapt.
First, let us say that a wind facility is 12.6 square kilometers in area (3,105 acres), which as a circle would have a radius of 2 km.
The area within 1 km of the facility would then be the area of a 3-km-radius circle minus 12.6 km², i.e., 15.7 km².
The area would be 37.7 km² within 2 km, 66.0 km² within 5 km, and 301.6 km² within 10 km.
If we then assume that the residential density is consistent throughout these areas, it is clear that there would be 4.2 times more families within 5 km than within 1 km of the facility, and 19.2 times more within 10 km.
Particularly with health effects, where not everyone is affected or affected to the same degree, a significant proportion of affected individuals becomes minuscule in the larger pool: If, say, 10% of the people within 1 km become ill after the wind turbines begin operating (in fact, it appears that the rate is much greater), that becomes only half of one percent of the people living within 10 km (ignoring for now anybody becoming ill farther than 1 km away).
Problem solved!
Also, as a commenter to the Wind Concerns Ontario noted, the physical effects of wind turbines fall off exponentially with distance, further ensuring a dilution to insignificance with a larger distance.
In contrast, if you compare that rate of 10% within 1 km with, say, a 1% rate farther than 2 km, it is very clear that the risk of adverse health effects is increased tenfold by living within 1 km of a wind facility compared with living greater than 2 km from it. But such studies have yet to be done.
