The Burlington Free Press ran an article this week that is perhaps the most comprehensive look at the emerging noise issues around Vermont’s two largest wind farms, in Sheffield and Lowell/Albany.  The problems at the Sheffield Wind project, which began operations in October 2011, are interesting, in that some residents live within earshot of I-91, yet have found that the sounds made by turbines 3/4 mile away are far harder to live with. (I, too, live about a mile from an interstate, hearing noise levels that are roughly the same as those I’d hear from turbines at that distance.)  A retired Air Force pilot says that the turbines remind him of a jet at 10,000 feet that never goes away.

Both projects must comply with state regulations that call for maximum sound levels of 45dB outside homes, and 30dB inside homes; quarterly monitoring at four locations is required as well.  The first year of monitoring at the Sheffield Wind project affirmed that it’s operating in compliance, though at least one monitoring location was close enough to the interstate that some have questioned its usefulness. 

The article highlights some of the challenges facing neighbors, as well as state regulators and wind farm operators.  For starters, we may again be seeing that turbine sounds of 40-45dB can be more bothersome than has been assumed, especially for people who, like one couple in the article, moved to the area “for its beauty and peace.”  Also, short-term sound monitoring may not occur at the times when the noise is most troublesome; the noise issues may not be solely related to wind speed and direction, but could also be affected by the level of inflow turbulence or other atmospheric conditions.  The article does not clarify how many complaints have been received around the Sheffield Wind project, but notes that 28 households have lodged formal complaints since the turbines on Lowell Mountain began operations in November.

A noise-reduction mode is available on the Lowell Mountain turbines, and Green Mountain Power is working to learn when it should be triggered.  Both sound testing and complaints from neighbors will inform that learning process.  “These noise issues are relatively new for us,” said Geoff Commons, director of public advocacy with the state Public Service Department. “We’re trying to figure out what the problem is. We’re trying to help.”

About a year ago, ten wind turbines began operation on Spruce Mountain in Woodstock, Maine, and as residents began arriving at summer camps at two ponds between three quarters of a mile and a mile and a half away, they found the turbine noise louder than they had been prepared for, as recounted in a July AEInews post.

Patriot Renewables brought in a sound consultant, who monitored noise levels at a home on Concord Pond, 1.6 miles from the closest turbines, for three weeks during August and September; the results were analyzed both by the consultant and the Maine DEP.  During this period, noise levels only topped the state noise criteria of 55dBA during the day and 45dBA at night when there were nearby sounds other than the turbines.  Turbine noise is reported to have varied between 23-32dB.

Neighbors were asked to report periods in which noise was bothersome, in order to identify any particular wind conditions that may be responsible.  Many (but not all) notifications from neighbors came when the wind was from the northwest at night; a hill to the north of the complaint locations may have shielded the area from wind, making the turbines more audible.

The state DEP consultant noted that turbines were most audible “late at night and in the early morning hours, when background sound levels can be well below 30 dBA. The residents who have filed complaints are evidently characterizing any audible turbine sound from Spruce Mountain Wind during those times as ‘high’ because at those times it is the most noticeable sound.”  

An Oxford Hills Sun Journal article includes more detail on the study, and affirms that some residents have said that it’s been difficult to go from the usual quiet or background noise of singing birds to the repetitive sound of turning blades.  This may well be a case in which noise levels are modest, but still more noticeable than residents had imagined they’d be.  Some pond residents had earlier noted that they were clearly audible on some days, and when at its worst, the noise drove them inside. The town has been considering a new wind ordinance for any future wind farms, in response to the complaints.  The Norway Advertiser-Democrat reported that Bob Elliot, Chair of the committee drafting the new ordinance, stated his group’s website had received “around 30 noise complaints,” but could not tell how many were from the Concord Pond community.  Nearby Shagg Pond is a bit closer to more turbines than is Concord Pond.