The past week has seen a flurry of new reports and articles that aim to debunk the idea that wind farm noise should be taken seriously as a concern when siting new wind farms.  AEI’s upcoming Wind Farm Noise 2011 report will address the issue in great depth when it’s released in about a week, but for now I wanted to make a few comments about the recent releases.

Two reports came from Canadian environmental groups that advocate expansion of wind energy and are frustrated by local resistance, especially in Ontario.  I share their support for wind energy providing an increasing percentage of our electrical generating capacity, and have little problem with the bulk of these reports; but in each case, I feel that their treatment of noise issues misdirects attention away from the very real problem at the core of the debate: when wind turbines are built closer than a kilometer or so from homes in rural areas, a high proportion of those nearby neighbors experience significant quality of life impacts due to audible turbine noise.

Sierra Club Canada released a 40-page report entitled The Real Truth About Wind Energy, while Environmental Defence published a 16-page overview entitled Blowing Smoke: Correcting Anti-Wind Myths in Ontario. Both reports begin with reassuring reminders that humans have used windmills for 2000 or more years, and evoke the pleasing image of dutch windmills; neither mentions that the nature of the noise coming from modern turbines is dramatically different than these historic designs.  In particular, as wind turbines get taller, they encounter a larger wind speed difference from the bottom to top of their rotation as well as more random air turbulance and fluctuations within the rotor diameter, both of which contribute to the at-times extreme pulsing or knocking quality of modern wind farm noise.  And while both affirm that low-frequency and infrasonic noise levels are moderate (generally below the threshold of average human perception), they don’t acknowledge the complex amplitude modulation that also occurs at these inaudible levels, which leads some low-frequency noise experts to suggest that they are likely to be perceptible at much lower intensities than the classic hearing threshold curves suggest (entirely separate from as-yet-unproven concerns about this affecting health, there’s little doubt it could make it harder to ignore the noise, increasing annoyance and quality of life impacts). The Sierra report goes into greater detail about acoustics, and while the information is largely accurate, they do of course draw from just some sources, and seem a bit too sure of some of their statements:

• They state definitively that turbine noise does not exceed 40dB beyond 500meters; this is clearly not the case in many situations (it reflects merely an idealized sound attenuation model, not real world experience).
• Likewise, the Sierra report suggests that aerodynamic noise has been significantly reduced in recent years, while in fact nearly all industrial turbines still produce sound levels of 100-110dB at the source, not much different than in years past. (100dB is roughly equivalent to a leaf blower or loud boom box, mounted high above the surrounding landscape)
• And while acknowledging that rural ambient sound levels are commonly as low as 20-30dB, they go on to state with unwarranted assurance that turbine noise at the Canadian allowed limit of 40dB would create minimal annoyance; in fact, many jurisidictions limit new noise sources to 6dB over ambient, because data shows that once it reaches 10db louder, it causes widespread complaints. (40dB will often be 15-20dB over night time ambient)
• Finally, they cite one of the well-known Scandinavian studies of annoyance levels, though the annoyance rates they mention include nearby neighbors who lease land and receive income from turbines.  The same paper states clearly that among non-leaseholders, annoyance spikes to 25% of those hearing 40dB and more.  In addition, this is but one of three studies by this research team; it took place in a location with a mix of rural and surburban locations, and its annoyance rates were lower than those of their purely rural study, which found annoyance rose to 45% at 40dB and over, very much in line with what many rural communities have found in recent years in the US and Canada.

The Environmental Defence report is less detailed, and stresses that noise from wind turbines cannot be clearly linked to any direct health impacts.  They again cite the Swedish data without correcting for rural populations.  To their credit, the ED report repeatedly stresses that those who do experience high levels of annoyance deserve respect, but by minimizing the rate of such disturbance at close ranges to turbines, they gloss over the primary public policy issue: how close should turbines go to homes?

I share ED and Sierra’s goal of expanding wind power generation.  Where i differ with them is that I feel that we should set siting thresholds at distances that insure that those closest are being minimally impacted.  I agree with their assessment that the majority of those living within sight, and occasional earshot, of turbines are doing fine, but the real-world evidence is becoming increasingly clear that in some communities (especially those with a high proportion of residents who are not working farmers/ranchers), turbine noise levels of 40dB cause significant quality of life impacts on a large minority or small majority of the closest residents. This fact should not be glossed over, and is a valid consideration as communities, provinces, and states settle on wind farm siting standards.

In Ontario, setbacks of 500m (1640ft) are the norm; this is designed keep sound to 40dB; in the US, it’s common to have smaller setback or higher dB thresholds, usually 45dB and sometimes 50dB. These will cause even more severe impacts on the closest neighbors.  Two recent in-depth articles have addressed this, from a couple of perspectives.  One, from the Forbes website, takes exception to recent reporting by Tom Zeller about the noise controversy in Vinalhaven, Maine. The author, William Pentland, frames his piece by saying, “I  do not want to trivialize the noise issue, which is a problem for a very small number of people who live in close proximity to the wind farm.”  Indeed it is.  By focusing the rest of his piece on critiques of these people’s experience and legal challenge, he may not trivialize the issue, but he basically ignores it.  He tries to “put this problem in perspective” by saying that  “many of the island residents who live as close or closer than those who have hired an attorney to represent them in regards to the noise issue are far more upset about the prospects of litigation that they are about the noise.”  Yes, a few close neighbors say they aren’t bothered by the noise, but somewhere around half clearly are, and others haven’t volunteered much about their experience, trying to steer clear of the tempest that’s roaring through town like a winter nor’easter. Pentland also highlights that two of the ten litigants challenging the local electrical co-ops handling of the noise issues come from “away,” which inspires many commenters to chime in on this always-ripe theme, neglecting the clear fact that the other eight are full-time residents.  Only a dozen or so year-round homes are within a half mile or so, where most of the noise issues are arising; this is exactly the situation that allows the noise issue to be painted as an issue affecting “a very small number of people,” while failing to raise the obvious next question: why not build them a bit farther away from homes??

The other recent lengthy article comes from Virginia, where wind farms are beginning to sprout.  It’s a very good read, nicely balanced (as indeed Zeller’s NYTimes piece was).  The author visits a community near one of Virginia’s first wind farms, where the closest resident is 3600 feet away from a turbine (this is just about the distance of the most distant of Vinalhaven neighbors who feel drastically impacted; in other words, if the Vinalhaven turbines had been this far from homes, there would have been few if any big problems). At the Virginia wind farm, this closest neighbor says, “to tell you the truth, at night, I like to listen to it.  It’s kind of a swoosh, but it’s pleasant.”  While visiting another neighbor, who lives three-quarters of a mile away, the author notes that the turbines are barely audible (it being the afternoon, not deep in the night, this means that the turbines are likely to be at least 40dB at this distance, much farther than the 1650 feet that Sierra Canada insisted they’d be at that level). The owner there notes that this was a relatively peaceful moment:  “the harder the wind blows, the louder they are,” he said. “Sometimes they will wake you up at night in the wintertime. There have been times when I turned the TV up a little bit” to drown out the noise.  (Note that this is inside the house with the TV already on, again indicating quite a high noise level, compared to projecttions: an inside noise level of at least 40dB, more likely 50dB).

The Environmental Defence report includes the following big-picture observation:

There is no doubt that the building of a wind power facility brings change to where it is located….A big part of the response to this situation must come from better practices by the Ontario government and wind power companies. More community-owned power projects must emerge to spread greater benefits to local communities. Earlier and better consultation with local communities must take place as projects are designed and implemented. Environmental assessments must be robust, and facility siting decisions done well. Communities must be real partners in development.

I would note that robust environmental assessments should include analysis of likely community reactions to noise increases caused by wind turbines, rather than simply noting the predicted noise levels. Such an analysis would look at increases over ambient and  the nature of the local community (working farm/ranch, vacation home, bedroom community, proportion of retired stay-at-home residents, etc., all of which contribute to whether new audible noise is likely to be acceptable to residents).  As with any environmental assessment, the presence of impacts doesn’t preclude going forward; rather, decision makers use this information as they decide what levels of impact are acceptable in the given location.

For more on AEI’s perspective on community responses to wind farm noise, see this column in Renewable Energy World:  this post about last summer’s DOE-sponsored NEWEEP webinar on wind farm noise; and this recent guest column, Wind Farm Noise: Moderate but Often Disruptive