Wind turbine noise is a complicated issue

picture of
~ wolfe Island ~
This is a letter to the editor written by Clif Schneider, a local expert on the topic of noise, in this letter he explains the concept of wind turbine noise and atmospheric stability something that needs to be considered carefully and is extremely important; Mr. Schneider has prepared a report in response to sound studies from commercial wind developers, (Acciona Spain) & (Bp British Petroleum), a series of background noise surveys were conducted , in Cape Vincent, NY between May and July 2008.
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Thousand Islands Sun, Letter to the Editor

~ By Clif Schneider ~

Some T.I. residents will be saying goodbye to those quiet summer evenings. There are now two wind turbine noise reports submitted by developers along the Thousand Islands corridor. One by AES-Acciona Energy concludes their project in Cape Vincent would not “create a significant noise impact.” PPM Atlantic Renewable, on the other hand, freely admits to Town of Clayton residents that their project “would be clearly audible.” In both cases, developers ignored the biggest potential noise threat from wind farm development — atmospheric stability.

First, we have to better understand wind and noise. When the wind blows, trees and shrubbery produce a lot of noise, enough to mask quieter sounds. When the wind subsides, other quiet sounds, like the sound of a cricket, can become more noticeable. This relates to wind turbine noise, too. Turbines are loudest when the wind is blowing hard. As wind subsides, turbines slow down making less noise. When the wind quits, turbines stop as well. However, there is a condition when turbines can still be noisy even after the wind stops blowing.

During clear, cloudless nights a process called radiation cooling takes place whereby the atmosphere next to the ground becomes stable — it decouples from the air mass just above the ground. What is significant about this decoupling is that there can be no wind at ground level, but the wind can be blowing quite hard at the height of a wind turbine. Here then is the worst-case scenario developers should be considering, turbines spinning loudly with no masking sounds close to the ground. Even worse, it can occur on summer nights with our bedroom windows wide open.

So, how frequent is atmospheric stability and how loud can the turbines get? From my review of Queens University survey, nearly forty percent of spring and summer nights could be associated with atmospheric stability. Therefore, atmospheric stability is notan infrequent occurance. In ground-breaking studies at a German wind park on the Dutch border, the Dutch physicist Dr G.P. van der Berg showed that “wind turbine noise could be up to 15-18 dBA higher than expected.” NYSDEC guidelines indicate that an increase of 15-20 dBA is “objectionable.”

In conclusion, we have the potential for a real problem. Participating landowners and local officials don’t know about this problem, but should. Developers know about the problem, but don’t want to deal with it. In any case, we should all discuss it before we make an unalterable decision that we might later regret, and if you don’t believe it can happen here, just visit Maple Ridge and talk to someone.

link here to Mr. Schneider's Report