Siting of Wind Turbines with Respect to Noise Emissions and Their Health and Welfare Effects on Humans 

This [document] presents an overview of the effects of large-scale wind turbines (greater than one megawatt) on people. It particularly addresses these effects with respect to residents living in the vicinity of wind turbine developments (often referred to as “wind farms”).

Of particular concern is the ability of the May 2010 Public Service Commission of Wisconsin (PSCW) sound and vibration guidelines [“Measurement Protocol for Sound and Vibration Assessment of Proposed and Existing Wind Electric Generation Plans,” May 2010] to protect the public health and welfare, and to do so with an adequate margin of safety [Environmental Protection Agency (EPA), Office Of Noise Abatement And Control (ONAC), “Information On Levels of Environmental Noise Requisite To Protect Public Health and Welfare with an Adequate Margin of Safety,” March 1974]. The three operative terms important to this discussion are:

• Welfare,
• Health, and
• Margin of Safety

In the present context the term welfare refers to the potential annoyance or nuisance effect of the noise. The word health refers to potential health effects of the noise having to do with sound level, frequency content, or temporal character. The term margin of safety relates specifically to the many unknown factors involved in predicting the health and welfare effects of wind turbine related sound. At present the A-weighted sound level is widely used in guidelines and regulations to place limits on residential sound exposure from industrial sources, and it has been used in wind turbine documents as well. The A-weighted sound level is a measure of a sound’s relative loudness. In the case of wind turbine sound it is not at all clear that many of the reported effects on humans can be explained by loudness alone. In fact, it is safe to say the scientific community does not know the exact sound exposure attributes that are causative to the health and welfare concerns of wind turbine sound. Until such time as a better scientific understanding of the cause / effect relationship becomes available, the margin of safety must include an uncertainty of estimation factor when using the A-weighted sound level, the C-weighted sound level, or combinations thereof.

A recent submittal to PSCW identifying concerns regarding the proposed PSCW May 2010 wind siting rules provides a good overview of the issues [PSC REF#:133746, “Comments by the Towns of Morrison, Wrightstown and Glenmore Brown County, Wisconsin, June 24, 2010.” Submitted to: Public Service Commission of Wisconsin, Docket No. 1-AC-231 Draft Chapter 128—Wind Energy Systems]. A number of points are raised, and rather than restate those relating to wind turbine sound emissions here I will say that I am in general agreement with:

• II.13 Siting Criteria, Items 1-4, 6-9, and
• II.14 Noise Criteria, Items 1-5.

Items not included above do not mean I am in disagreement with them. They simply contain language in whole or in part that exceeds my area of expertise.
The remainder of this report presents comments on the following topics:

1. The nature of wind turbine noise compared with other noise sources heard in residential communities.
2. Community noise standards and how they apply to wind turbine environments.
3. The reported effects of wind turbine noise on people in residential settings.
4. The paucity of information regarding why people respond as they do to wind turbine noise.
5. The sound levels above which residents appear to begin experiencing these effects.
6. The setback distances from wind turbines below which residents appear to begin experiencing these effects.
7. Policy Question.
8. Some concluding remarks.

Throughout my presentation my focus will be on the health and welfare of those who may be exposed to varying degrees of wind turbine noise. This emphasis is consistent with the seminal 1974 Environmental Protection Agency (EPA) document, “Information On Levels of Environmental Noise Requisite To Protect Public Health and Welfare with an Adequate Margin of Safety.”

06 July 2010

Richard D. Horonjeff
Consultant in Acoustics and Noise Control
Boxborough, MA 01719

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