Tall wind turbines in concert with each other, especially those sited on prominent ridgetops, create profound noise reverberations extending out for more than a mile, sounding like "a boot tumbling in a dryer" or the revving of jet engines on a runway. It is very difficult to predict noise levels in the mountains compared to flat land. Noise levels will be amplified in some areas and diminished in others depending on the shape of the terrain, the wind direction, the changes in wind velocity, and so on.
The impact on people also depends on whether wind turbines operate in synchronization and whether the noise "beats" or throbs. This also depends on wind direction and velocity. Who will get bombed? Who knows? That is likely very hard to predict. The travel of sound waves and their behavior is similar to the way water waves travel. Most of us have seen how water behaves when waves enter into a gap or a split or channel of rocks in the ocean. The waves travel inward and pile up-and-up as the channel restricts them. The more the channel narrows, the greater the piling of the wave. Sound behaves in the same way. The more it piles up, the louder it gets.
A letter from Meyersdale, Pennsylvania resident Bob Laravee, who lives 3,000 feet from the windplant, documents how he measured the noise over a 48-hour period. The results "showed an average reading of about 75 decibels during that period." "According to the EPA, noise levels above 45dB(A) disturb sleep and most people cannot sleep above noise levels of 70 dB(A)." Turbine noise is so irritating and disconcerting that it often causes people to seek medical attention, as Rodger Hutzell in Meyersdale had to do. Wind leases typically contain "noise easements" to protect the company from liability.
Noise from European windplants is a notorious and well-documented nuisance there. The wind industry is very aware of this problem but often tries to "hide" it by taking visitors during the day directly under the turbines where there is typically little noise or by conducting tours from May-September when wind speeds are typically lower.
A leading acoustical researcher of the noise problem, G.P. van den Berg of the University of Groningen in the Netherlands, believes loud aerodynamic sounds are generated when the moving propeller blade passes the turbine tower mast, creating sound pressure fluctuations. Such fluctuations may not be great from an individual turbine, but when several turbines operate "nearly synchronously, the pulses... may occur in phase," significantly magnifying the sound. Van den Berg also notes a "distinct audible difference between the night and daytime wind turbine sound at some distance [more than one mile] from the turbine"—a finding consistent with the experiences of Meyersdale residents. (Both quotes were taken from G.P. van den Berg, Effects of the Wind Profile at Night on Wind Turbine Sound: Journal of Sound and Vibration (November 2004) 277:955-970.)
The problem is so acute and well documented that the First International Conference on Wind Turbine Noise was held in Berlin, Germany on October 17 and 18, 2005. Organized by INCE/Europe in collaboration with the European Acoustics Association, the conference addressed "Wind Turbine Noise: Perspectives for Control"
A New York physician, Nina Pierpont, has called the phenomenon, Wind Turbine Noise Syndrome; her book on the subject will be available to the public soon.
Regulatory agencies and county zoning ordinances should insist upon acoustical field research to assess this noise phenomenon, requiring independent measurements and interviewing nearby residents. They should pay particular attention to noise measurement averages. Averages would not mean much if they were applied, say, to residents living next door to an outdoor pavilion during a rock concert. And it will not mean much to the residents of a rural community, either—who are used to the enjoyment of a quiet landscape.
An exemplary noise testing protocol for windplants was recently approved as part of the Shawano County, WI wind ordinance. Other polities should strongly consider adopting this standard to protect citizens from windplant noise. This county had been targeted for industrial wind development and the citizens there, aware of problems with wind technology, vowed to protect the public by establishing regulations and testing protocols that the wind industry and enabling agencies now must follow.
Other nuisances industrial windplants may cause are:
- Shadow Flicker and Strobe Lighting. When turning with the sun behind them, turbine blades cast moving shadows across the landscape and into houses in ways that may affect surrounding properties at a considerable distance; these are commonly described as a strobe effect within houses that can be difficult to block out. "Some people lose their balance or become nauseated from seeing the movement. As with car or sea sickness, this is because the three organs of position perception (the inner ear, eyes, and stretch receptors in muscles and joints) are not agreeing with each other: the eyes say there is movement, while the ears and stretch receptors do not. People with a personal or family history of migraine, or migraine-associated phenomena such as car sickness or vertigo, are more susceptible to these effects. The strobe effect can also provoke seizures in people with epilepsy." (Nina Pierpont, in a personal conversation. Dr. Pierpont was formerly a clinical professor of pediatrics at Columbia, University and is now in private practice in Malone, New York).
- Lightning and power surges. Wind turbines themselves may cause irregularities in the power supply as wind speed changes. Within the power grid, supply and demand must always be balanced; there is no storage of electricity on this scale. When the wind dies, there is less power (brown-out) until a plant using a more reliable resource powers up to increase production. When the wind gusts, there may be power surges. Residents living near the installation in Meyersdale, which came on-line in December 2003, have had to replace stove elements and small appliances due to power surges which started at that time. Residents of Lincoln Township, Wisconsin, near a wind installation noticed an increase in power surges associated with lightning strikes in their area after the turbines went on-line in June 1999. [Two computers protected by surge protectors and a TV set, all in different houses, were simultaneously "fried" one evening when lightning struck a nearby wind turbine tower.]
- Shoddy site construction practices can also cause serious erosion problems, especially if built along steep slopes. There is much documentation about how turbine blades throw bolder-sized ice that has accumulated on the blade surface during winter. There are documented—and very dangerous—fires caused by malfunctioning turbine equipment.
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