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Windy study gives mixed results on turbine noise  

Credit:  By Chris Aldridge, Tribune Staff Writer | Huron Daily Tribune | Saturday, January 10, 2015 | www.michigansthumb.com ~~

HURON COUNTY – The results are in.

The question: Does noise from wind turbines exceed limits set in the county’s wind energy ordinance?

Yes, and no.

That’s essentially what results show from a more than $20,000 nighttime noise study paid for by the county and conducted at four locations by an independent Grand Rapids acoustics firm.

While noise from wind turbines did exceed allowable limits, the loudest sound actually came from traffic, according to the report from Acoustics by Design (ABD).

When the county interviewed acoustics firms for testing at wind turbine sites, both said the county’s current wind ordinance has major deficiencies and is outdated. Commissioners also have fielded similar complaints from constituents.

In August, when commissioners hired ABD, County Commissioner David Peruski said people in their homes are having problems with infrasound or low-frequency sounds. Infrasonic sounds are those with frequencies less than 20 hertz, which is the lower limit of human hearing. Some studies show effects from the infrasound emitted from wind turbines contribute to nausea, headache and sleep disturbance, while other studies show there is no risk to human health.

“So far, that doesn’t seem to happen,” Peruski said of potential problems with low-frequency sounds in Huron County, after reading the report.

Huron County’s wind energy ordinance sets maximum levels for audible sound from wind turbines.

ABD notes audible sound occurs over a wide frequency range, from about 20 to 20,000 hertz. Because human hearing does not respond equally to sounds at different frequencies or pitch, the firm applied a frequency weighting to the measurements, giving the decibel reading a dBA abbreviation, the report states.

According to the ordinance, for those within a wind district, sound pressure levels shall not exceed 50 dBA or the ambient sound pressure level plus 5 dBA, whichever is greater, for more than 10 percent of any hour, measured at any residence. For those not participating in a wind project, the maximum is 45 dBA for any residence, school, hospital, church or public library.

“Was the 45 (dBA limit) exceeded? Yes,” Peruski said. “But by five or more? No. To say it’s within 5 (dBA) of the standard … that could meet the ordinance.”

Of the four locations tested, wind turbine noise was highest at 4297 Stambaugh Road in Ubly, according to the report.

“The wind turbine noise was more prominent here due to the (wind turbine) proximity and lack of other background noise sources,” the report states.

At 6829 Sebewaing Road in Owendale, noise from the wind turbine was lowest of all measurement locations, the report states. However, higher ambient sound levels from multiple trucks passing by brought a reading of 80 dBA. It helped offset and bring in compliance the 49 dBA recorded from turbines during testing, Peruski said.

And because most locations were near “fairly busy roads with multiple vehicle passbys,” the report shows traffic noise contributes considerably to ambient sound levels.

The results didn’t come as a surprise to Peruski.

“I don’t recall seeing anything terribly high,” he said.

But he said he is hesitant to give a clear yes or no as to if turbines are indeed exceeding noise levels set in the current ordinance.

The study may, however, help develop sound testing methodology for future wind projects, he said.

“I believe it has enough data in it that we need to take a look at what our ordinance says and how it is stated,” Peruski said.

Talks of a moratorium on wind energy development and the process of reviewing the county’s wind ordinance hinged at least partially on the study results.

The county is still waiting for a final draft from ABD, which will suggest regulations on noise from wind turbines that the county can include in its ordinance. A committee tasked with amending Huron County’s wind ordinance will review the study and make a recommendation to the planning commission, which will then forward that to the board of commissioners.

The firm says measurements were completed overnight on Nov. 13 and Nov. 14. They were taken in hour-long increments. Ambient noise also was measured in Ubly on Nov. 14, according to the report.

The firm set a tripod 5 feet above the ground and used a sound level meter to take measurements either on the property or crop line at the location nearest the closest wind turbine. As noted by ABD, the county’s ordinance does not specify the type of measurement equipment to be used. Wind speeds varied from about 3.5 to 8.5 mph during testing under overcast skies.

Source:  By Chris Aldridge, Tribune Staff Writer | Huron Daily Tribune | Saturday, January 10, 2015 | www.michigansthumb.com

This article is the work of the source indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.

The copyright of this article resides with the author or publisher indicated. As part of its noncommercial effort to present the environmental, social, scientific, and economic issues of large-scale wind power development to a global audience seeking such information, National Wind Watch endeavors to observe “fair use” as provided for in section 107 of U.S. Copyright Law and similar “fair dealing” provisions of the copyright laws of other nations. Send requests to excerpt, general inquiries, and comments via e-mail.

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