Research summary of Francis, C.D., Ortega, C.P., Cruz, A. 2011. Noise pollution filters bird communities based on vocal frequency. PLoS ONE 6(11):e27052.

An ongoing research project in New Mexico continues to shed more detailed light on the question of how moderate human noise affects nearby wildlife.  In a study design that effectively separates out the impact of the noise from other habitat disruption effects, Clint Francis and his colleagues are finding that some species are displaced, while others seem to thrive in areas with coalbed methane compressor stations creating noise around the clock.  The most recent paper to be published by Francis et al finds that species that sing at lower frequencies are most likely to avoid the noisy areas, while those who vocalize at higher frequencies are more apt to be unaffected or even thrive.

While this research studies an area with oil and gas development noise, it’s likely that similar effects would occur in and near wind farms, which also produce predominantly low-frequency noise. And, as the authors note to conclude their paper: “At the community-level, we must still determine whether noise is an agent of ecological filtering for other taxa that rely on acoustic communication.”

Rather than doing the full AEI lay-summary of the most recent paper, I want to point you to the great summary already written by Caitlin Kight, biologist who studies the effects of anthropogenic disturbances on animals; it was recently featured on her Anthrophysis blog.

Town officials from Mount Pleasant, Wisconsin recently visited a wind farm in Brownsville in order to listen and take sound measurements of turbines similar to three being proposed by a local plant that aims to generate all its energy needs on site.

What they heard reassured them, after hearing noise concerns from some local residents. “At 800 feet, measurements came in at 46 – 47 decibels, and at 1,200 feet it was less than 40 decibels, ” said Planning Director Ron Meyer. By comparison, he said a passing car on the paved road came in at 62 decibels. Even within a thousand feet, they could sometimes not hear the turbines spinning.

Of course, any quick visit to a wind farm offers just a snapshot view (or listen). In many cases, neighbors’ noise issues occur mainly in particular atmospheric or wind conditions, so the question becomes how common these above average noise events are. Stable sound-reflecting air layers above the turbines, high levels of turbulence in the air hitting the blades, and wind speed differences from the bottom to top of the blades are all factors that tend to contribute to higher or more intrusive noise levels. And, night time noise tends to be a bigger issue than day time; even moderate noise levels can become the loudest sound heard out a bedroom window at night.

Still, it’s good to get out there and get a sense of what may be heard near the proposed turbines.  Unfortunately, no residents were able to join the town officials on this trip, though they were invited. It’s hard to know what degree of investigation will really give a complete picture of what may be experienced by people near the plant; spending a few nights in Brownsville might help.  More generally, many towns considering wind project siting questions would be well served by a series of well-designed survey projects around wind farms, which might best capture the range of experiences at existing wind farms.

A couple living roughly 5000 feet from a proposed 5-turbine wind farm has appealed the project’s approval by the town of Clifton, Maine, citing quality of life concerns due to the likelihood that they will hear the turbines from their home and farmlands. “Our land is our home. We work here. We farm here. We recreate here and we restore our souls here,” said Peter Beckford.  Beckford and his wife Julie run an organic flower business on a sixty-acre property, which also includes several small cabins where farm apprentices and other visitors live.

The proposed wind farm, on Pisgah Mountain, was designed to include 4000-foot setbacks from homes, but the Beckfords say that their cabins and other buildings used for their business were improperly excluded as protected or occupied structures when the setback was applied.

The Beckford’s challenge is notable in that it is making a quality of life argument that audible turbine noise is an inappropriate addition to the local soundscape.  The appeal rests on several permitting issues, including the outbuilding distance and other aspects of the town’s planning process, but their statements indicate that the turbine noise is the crucial issue for them.  Their challenge is perhaps the strongest expression yet of the feeling by some rural residents that any noise intrusion is unacceptable; several more cautionary acousticians have recommended noise limits, at least at night, of 30-35dB, and setbacks of a mile to a mile and a half, in acknowledgement that any turbine noise readily audible above quiet rural background sound levels will trigger significant annoyance in some neighbors.

Most previous challenges of wind farm approvals have attacked siting standards that placed turbines much closer than a half mile, or noise standards that could allow intrusive sound levels (15dB or more over ambient) at some or many homes. In saying that three-quarters of a mile is not far enough away, the Beckfords are standard-bearers for rural residents who want wind farms to be far enough away to be effectively inaudible. For people living deep in rural areas, it’s an understandable desire; some towns have have banned tall industrial turbines altogether, to assure local soundscapes will remain unblemished.  Other towns, aiming to be somewhat more welcoming to wind projects, have set half-mile to 4000-foot setbacks in order to reduce the severity and frequency of noise intrusions. Time will tell whether new wind farms built with these larger setbacks will be more easily accepted by rural communities.

A wind farm in South Australia has been shutting down 16 of its 34 turbines at night since last December, after a nearby neighbor complained of noise keeping his family awake at night.  This week, the state Supreme Court affirmed that the wind farm was breaking its noise limit, due to a tonal noise component, and sent the issue to the Environmental Resources and Development Court for adjudication.

The neighbor, Bill Quinn, said his mother and sister, who live near the existing turbines, had been in “absolute heaven” since the decision was made to shut the turbines down at night. A spokesman for AGL Energy said that “We understand that one of our neighbours has been inconvenienced and we apologise. We want to be a good neighbour and we’re committed to working with local communities and taking any concerns that they have about our projects seriously.” AGL is working with the turbine supplier on a “permanent acoustic treatment” to dampen tonal noise.

Several Australian states have recently moved to increase setbacks from new wind farms.  In Victoria, the Baillieu government has announced strict regulation of wind farm developments, including a minimum 2km (1.25mi)  distance from houses. In NSW, Premier Barry O’Farrell has indicated he intends to introduce similar laws. South Australia’s guidelines limit noise to 35dB in areas “primarily intended for rural living” and 40dB elsewhere, while providing for agreements with landowners to allow higher sound levels.

Town votes in Riga, Michigan, and Rumford, Maine have both adopted wind farm siting standards that are somewhat more cautionary than most. Riga township  voted 440-236 to uphold an ordinance that establishes setbacks of 4x turbine height (1200 or so feet) from non-participating property lines, and sets a noise limit of 40dB at night and 45dB during the day.  The distance setback shouldn’t be an issue for developers (1200-1500 foot setbacks are typical of many wind farms), though the night time noise limit could make it difficult to site turbines closer than a third to half mile from homes. It wasn’t clear from initial press reports whether the Riga ordinance provides an option for neighbors to sign waivers allowing closer siting or higher noise levels.

Meanwhile, the third time was the charm in Rumford, where two previous proposals went down to defeat, one for being too stringent (including setbacks of a mile), and the next for not protective enough (the sticking point likely being a 45dB night time noise limit).  The current proposal garnered overwhelming support, winning by a margin of 1137-465, and includes a 40dB night/50dB day noise limit, along with a 4000-foot setback from non-participating neighbor property lines.  Neighbors can, however, sign a Mitigation Waiver agreement to allow closer siting.

Conversely, in New Hampshire, Read the rest of this entry »

I’m traveling this week, so not monitoring the news on a regular basis, but tonight I thought it would be useful to simply highlight a few news items that came through my custom Google News section on wind farm noise in the past few days.  The mix of stories is pretty typical of what occurs each week:

Representing the widespread efforts of local planning authorities to make sense of conflicting voices are two towns, one near the end of its process, and one still close to the beginning.  Supervisors in Palmyra Township in Michigan (right) decided to rescind an earlier tightening of their noise and siting regulations, after a wind developer said the rules as adopted would likely prohibit construction in the town. In a 3-2 vote, the majority were concerned about such a prohibition, agreeing with Supervisor Dale Terry, who said, “I’m not sure that is fair or proper,” while one joined with Steve Papenhagen, who stressed that “I don’t know how we can force this on landowners that don’t want to be a part of it.” The Supervisors re-established a noise limit of 45dB at buildings on neighboring properties, up from 40dB in the previously amended plan.

In Frankfort, Maine, where a four-to-six turbine project is planned, a community meeting on a proposed wind farm ordinance got heated, culminating in a shouting match between a developer and an anti-wind activist outside the building after the meeting ended. (Apparently, they embodied the state of our current dialogue to perfection, each yelling that the other was a liar!) A committee that had developed a draft ordinance presented it at the meeting; they proposed a 1-mile setback, and noise limits of 45dB during the day and 32dB at night, measured at neighboring property lines.  State regulations currently call for 55db during the day, and a recently proposed 42dB at night, measured at homes. Josh Dickson, who served on the committee, noted that noise heard at homes, especially at night, can cause insomnia and hypertension, according to their findings. “At the end of the day, this is research. It’s not perfect. Neither are we,” Dickson told the crowd. “We did the best we can. The decision will be up to you guys, not us.” The small wind developer planning the project, Eolian Renewable Energy, is proposing a setback of three times the height of the turbines, or about 1000 feet, and also calls for using the state noise limits.

A woman from Freedom, Maine, spoke at the Frankfort meeting, and shared an unusually clear and poignant story of noise impact at their home, 3000 feet from one of several turbines.  Her three kids have all been prescribed sleeping pills due to wakefulness since the turbines began operating; this strikes me as particularly noteworthy, since the kids are less likely to be affected by pre-existing concern or fear, which some blame for the reports of sleeplessness and stress in adult wind farm neighbors.

In North Devon, England, the Fullabrook wind farm (left) is gradually becoming operational, with all turbines planned to be spinning by the end of November. Several neighbors have noted that noise has been a problem as the wind farm begins to ramp up. Sue Pike’s bungalow is 600 meters (about 2000 feet) from one of the turbines at the new wind-farm and she says: “It is dreadful – the main sound is like a huge great cement mixer going around – then you get the loud whoosh and also whistles and hums. Altogether we have counted four different noises coming from it. Back in the warmer weather when the turbines were being tested we couldn’t open the bedroom or lounge windows – fortunately we are double-glazed so that helps cut out the noise – but we were stewing indoors.”

The wind developer in Devon, ESB, will begin noise monitoring once the wind farm is fully operational. “ESB will continue to work closely with the local community – particularly our immediate neighbours and North Devon Council – to ensure we not only meet all conditions of the planning permission, but that we are able to discuss local concerns and take what measures we can to address issues,” commented a company spokesman. North Devon Council’s Environmental Health Department will also conduct site analysis at five locations in response to residents’ concerns.

On the other side of the coin, Barnstaple town councillor and Green Party member Ricky Knight visited a friend’s house near the wind farm (though the distance wasn’t specified), and said, that “essentially all we heard was the wind, birds and farm machinery. I was not able to discern any sound coming from the turbines. I am in receipt of criticisms (from people who don’t like the wind-farm) but I get far more support from people who simply register confusion about this subject.”

While it’s quite common to hear from wind farm supporters who were surprised and dismayed by the noise levels they encountered once the turbines were operating, we hear the opposite tale from Leicestershire, UK.  There, after living for seven months with a new wind farm, some opponents are saying it’s not as bad as they feared it would be.  The article quotes two former objectors and one wind turbine host and doesn’t specify many distances, but one farmer “less than a mile” away says “I went to all the protest meetings and I was against them from the start. But now, I must say they don’t really bother me. I can’t hear them and I can barely see them. It’s like the industrial revolution all over again – people don’t like change until it actually happens and they get used to it.” This could be a simple case of people a fair distance away being more worried than they needed to be; a quick search online didn’t come up with news reports of problems from other (closer) residents, but it may be too early to assume there are none, especially since they’ve yet to go ’round all the seasons.

Knight’s experience in Devon, as contrasted with Pikes, is a great illustration of the disconnect that continues to dog wind farm development and ordinance-writing. I think we can safely assume that Pike’s not imagining the sound that’s bothering her, and that Knight visited at a time and place where the turbines were inaudible (and it must have been daytime, since farm machinery was operating). Complicating the challenge before town boards is a widespread uncertainty about who to trust; as noted by Palmyra Supervisor Jim Isley, “I have to wonder sometimes if one side doesn’t exaggerate their claims, and the other side perhaps doesn’t tell all that they know.” Indeed, AEI’s continuing attempts to make sense of the polarized rhetoric coming from the two sides suggest that both tend to overstate their case. Developers often downplay potential noise issues; for example, the Eolian website lists typical rural sound levels at 40dB (probably a 12 or 24 hour average), while night time sound levels in deeply rural areas are often measured as low as 20dB, so that a turbine may become a truly dominant sound. Meanwhile, community groups tend to assume that the worst-case responses they hear about elsewhere will be common, even at great distances. For example, a letter published this week about a proposed wind turbine at a gravel plant in California, expressed concerned that a school is “only 1.5 miles away.” The letter claims that Oregon requires a two-mile setback (they don’t: though their noise limit is one of the lowest, 36dB, setbacks tend to be in the half-mile to mile range). Even many more cautionary acoustics experts, who tend to favor noise limits of 30-35dB, suggest that 2km (1.25 miles) is a reasonable minimum setback, with some recommending a mile and a half; the gravel plant turbine doesn’t appear to be close enough to warrant alarm or heightened concern. We clearly have a long way to go before we can have a clear, reasoned discussion about whether current setback standards are providing a degree of community noise protection that’s similar to that we’ve become used to from other noise sources.

A brief article from a local paper in Illinois shed some new light on two key issues that have come up in many communities considering new wind farm proposals.  The meeting of the Lee County Zoning Board of Appeals featured an hour-long presentation from Carl Phillips, an epidemiologist who has published a peer-reviewed study saying there is “overwhelming evidence” of health effects near turbines. He said that people up to two miles away have reported health issues such as sleep and stress issues and mood disorders.  When asked what percentage of residents report health problems, he said that there have not been solid studies of that, but that his best guess, based on what research has been done, is about 5 percent of those within a mile or so. This relatively low estimate may surprise some, but such reports from many wind farms lead Phillips to conclude that anyone denying health effects exist is ignoring the evidence or “trying to mislead.” And, even this low estimate was challenged by representatives from Mainstream Renewable Power, who characterized Phillips’ presentation as “personal hypotheses.” (Ed. note: the continuing effort of industry representatives to discredit suggestion of any problems at all, including Phillips’ modest 5% estimate, or recordings that reflect higher levels of sound or amplitude modulation than expected, has become a major impediment to constructive engagement on wind farm siting decisions; ongoing diligent study by more cautionary experts deserves to be given more credence.)

In addition, the mayor of the village of Lee asked representatives of Mainstream whether confidentiality agreements signed by landowners leasing land for turbines will prevent them from discussing any health problems that they may notice once the turbines are operating–reflecting a widespread concern that health problems may be under-reported due to such agreements.  One Mainstream rep spurred laughter from the audience when he said he couldn’t talk about what the confidentiality agreements address, since they’re “inherently confidential.” But another Mainstream rep stressed that the agreements do not preclude talking about health. (Ed. note: Many confidentiality agreements with landowners are primarily designed to keep financial details private; this is especially true when a house is bought by developers.)

For the past three years, I’ve been learning what I can about the ways that wind farm noise affects nearby neighbors.  While most online information tends toward the black-and-white—the sound levels are lower than most human noise sources and current siting standards are fine; the noise is invasive and we need to totally rethink the efficacy of wind energy—AEI has been dedicated to fleshing out the shades of grey. A noise that drives one person crazy is considered a gentle whoosh by another; ranching areas tolerate wind farm noise at levels far above those that are causing problems in rural areas where residents especially value peace and quiet; community noise standards that minimize complaints about, say, road noise, can appear to be too high for wind farms.  As important as it is to tell the whole story, including the fact that much is yet unclear, I feel a bit adrift in the grey these days. When it comes right down to it, how does one describe a shade of grey?

In the coming months, AEI is going to take a different approach.  More to the point, I’m going to focus my energies toward a different purpose, a new task.  Rather than trying to “tell the story” in a way that helps everyone see the issue from a larger perspective, I’m going to use my time and energy to put together a toolkit aimed at providing the necessary information to allow anyone to come to their own conclusions: an annotated collection of concrete information about the sound levels and varied community responses observed around wind farms. Given the limits of what one person can do, it probably won’t be totally comprehensive, but it will draw from the full spectrum of researchers and experiences, and will attempt to provide some context to understand what is known, what is mostly unknown, and where we might most fruitfully direct further investigations.

I think that AEI’s publications over the past couple of years have done a fairly decent job of telling the big-picture story of wind farm noise. The various presentations, articles, and reports have taken different approaches toward a common goal: to explore the paradoxes and subtleties that belie both the black and the white views.

Read the rest of this entry »

AEI Commentary

The wild and turbulent public debate about wind farm noise issues continues to generate steady new eruptions in Ontario.  And while what’s coming out could be extremely valuable information for others struggling to support a more cautionary approach to wind farm siting, media reports are contributing to an increasingly jumbled public perception about the troubling health impacts that some wind farm neighbors have experienced.

Ironically, the spotlight currently shining on Ontario could be shedding a clear, focused light on the shortcomings in current siting standards – even Ontario’s relatively stringent ones. That light would reveal regional regulatory staffers raising concerns about whether the standards as currently applied are in fact protecting residents from undue disruption by wind farm noise, increasing anecdotal evidence from homeowners and realtors that wind farms make it harder to sell homes at their fair value, and telling examples of homes bought at market value by wind developers and later sold at large losses.  Instead, these important and fascinating stories are being jumbled into a far less coherent mess of public perception, with negative health impacts becoming the dominant theme. (See the final paragraphs of this post for AEI’s prescription for moving forward more constructively.)

As real as the health effects can be — there’s no doubt that some nearby neighbors have struggled mightily with them, to the point of leaving their homes to find relief — it doesn’t serve the public to conflate every noise complaint with a health complaint, or to distort the sources of noise complaints to make the suffering of the most afflicted appear to be far more widespread.  This is, unfortunately, the effect of recent media reports from Ontario, Read the rest of this entry »

Ontario is definitely at the heart of current controversies over wind farm siting.  While an environmental tribunal ruled against a health-based appeal in July, allowing the 8-turbine Kent Breeze Wind Farm to continue operating, many of the same issues will soon be argued in court.  A local family that lives just over 1.1km (just under three quarters of a mile) from the nearest Kent Breeze turbine has filed suit against three companies behind the project, saying that since the wind farm went operational in May, they’ve suffered from vertigo, nausea, and sleep disruption, and more to the point, that the developers knew this could happen.

“Within two weeks of them starting up I was in the emergency. I was dizzy and unable to stand. I was given medication and it has been four months and it hasn’t gotten better. I get motion sickness and light headed,” said Lisa Michaud. “At night I’m afraid to lie down because of the constant vibration and spinning.”

At the heart of the court case is the claim that the possibility of health impacts is known to exist, and indeed, parts of the report from the tribunal appeal which lost last month are called on to affirm this:

“This case has successfully shown that the debate should not be simplified to one about whether wind turbines can cause harm to humans,” the Environmental Review Tribunal stated in a report on the Kent Breeze project. “The evidence presented to the tribunal demonstrates they can, if facilities are placed too close to residents.”

In essence the Tribunal ruled that existing Provincial siting rules are sufficient to meet the threshold it imposed; these rules call for at least a 550m setback from homes, about half of what the family filing suit is living with. As reported in detail on AEInews at the time, the Tribunal report is a fascinating overview of the current state of the wind farm noise issue, with long summaries of expert testimony from both sides. The tribunal, while affirming the value of ongoing research into health effects and the nature of wind farm noise, ruled that the more cautionary evidence remained “exploratory,” rather than “conclusive,” and set a threshold for ruling that would require that the wind farm “will” cause “serious harm.”  Short of that, the Tribunal ruled that it could proceed. It seems likely that the court will be asked to review much of the same conflicting testimony; I am not sure whether the legal thresholds are different there than in the Tribunal process.

Meanwhile, the wind boom in Ontario has become a key issue in the current provincial election campaign, with both the candidates taking opposite stands and citizens speaking against current siting standards province-wide. Since the current Liberal government sponsored the Green Energy Act and its current standards, much of the opposition takes a decidedly conservative edge, often including opposition to government support for renewable energy in general and wind energy in particular. It certainly goes far beyond noise concerns for many of the most vocal opponents, with health impacts joining more generally conservative principles in arguments being made. One woman who has had to move from her home recently told a rally that the Liberal government is “denying” the health impacts of turbines and “ignoring” the people who are suffering. “People just aren’t going to sit back and take it anymore…We’re going to have your government so low, so low, so low, you’re not going to get elected. It’s as simple as that.”

Meanwhile, Liberal candidates including current leader Dalton McGuinty note that the standards are among the world’s most precautionary, and refer to a 2010 provincial report that focused on direct health impacts: “I rely on our chief medical officer of health here in Ontario to tell us what’s safe for our families,” McGuinty said Thursday. “What we have heard, of course, is doctors [and] nurses for 20 years now, they’re saying you got to shut down coal-fired generation in Ontario.”

The Maine Board of Environmental Protection has approved new wind farm noise standards that will lower night time noise limits to 42dB at the property line of any nearby homesites, a 3dB reduction from the old standard.  The daytime limit of 55dB remains unchanged.  Community groups, which initiated the review with a formal citizens proposal, had encouraged a standard of 35dB. The new rules will need to be approved by the state legislature in January.

Read new rules in full. (note: first half includes markup edits; second half is final version)

The new rules also include detailed procedures for measuring noise and establishing compliance with the noise limits. In the fine print, there is one provision that appears to add noise protection for neighbors, and some that raise questions.  The additional protections include a 5dB penalty if there is moderate blade swich (amplitude modulation) present; any repetitive pulse of sound of 5dB or more will trigger this penalty, meaning the average sound will then need to be 50dB during the day and 37dB at night.

The criteria for establishing compliance raise some questions. Read the rest of this entry »

The State of Victoria (Australia) has enacted new wind farm siting guidelines that prohibit construction within 2km (1.25 miles) of a home unless the owner has signed off on the nearby turbine(s). In addition, the new guidelines prohibit wind farms within 5km of many existing villages, in order to allow for future growth.  And, several areas with “a high degree of amenity, environmental value, or are a significant tourist destination” are excluded from development. (In Australia and New Zealand, the term “amenity” is often a factor in planning decisions; it largely corresponds to what we might also term rural quality of life.)

The new guidelines set a 40dB noise limit, reduced to 35dB in areas of “high amenity.”  It may be of interest to note that the Victoria planning authorities seem to equate 35dB to about a 2km setback, whereas an Oregon noise standard of 36dB has more often led to roughly half-mile, or 1km, setbacks.  It appears that the noise modeling is using different parameters in Oregon than in Victoria.  It’s also possible that the 2km buffer is designed to protect “visual amenity,” with the noise limit being a secondary feature of the guidelines.

Already, some wind farm developers have cancelled plans to build in Victoria, while locals who have experienced quality of life or health impacts praise the moves. I was especially struck by the reports of Adrian and Helen Lyons, who have 15 turbines within about 3km of their home, with the closest about 1.7km (just over a mile) away; both have reported a feeling of sustained pressure in their ears when the wind comes from the north.  The ear pressure has disturbed their sleep.  This spurs my ongoing question as to whether some of the physical sensations may have more to do with air pressure downwind of turbines, rather than noise levels.  To my knowledge, factors creating pressure differentials have not been investigated, although the related investigation of turbulence effects is on the research agenda of agencies and companies seeking to optimize turbine layout in wind farms.

See this site to download the new Victoria wind planning guidelines.  Or, see this Advisory Note summarizing the new amendments, and this PDF of the full planning and policy guidelines.

The Willow Creek Wind Farm has been given a reprieve from needing to address noise violations, as the Morrow County Court (the local name for county commission) decided not to enforce the state noise law.  Oregon has some of the most stringent noise standards, 10dB over night time ambient, which amounts to a noise limit of 36dB; the commissioners decided that the noise violations were minor and rare enough that they would not enforce them, a decision that was largely spurred by the fact that the state has abandoned its noise control enforcement efforts in 1991, leaving enforcement of the state standard to local authorities.

As covered previously on AEInews, dueling sound studies presented very different pictures of the noise violations.  An Invenergy study showed rare violations, but did not study sound at high wind speeds; a sound study by local residents showed excess noise especially at high wind speeds, with one home experiencing noise over 40db on the majority of nights.

“I’m flabbergasted,” said Jim McCandlish, a lawyer for three of the neighbors, after the vote. “The county court has an obligation to protect the health and welfare of its citizens.” McCandlish said his clients’ constitutional right to due process was being denied, and said the neighbors intend to appeal the decision to Oregon Land Use Board of Appeals.

The County’s actions were in part a response to a ruling by LUBA in June that questioned the county’s interpretation of the 36dB noise limit. In its ruling, LUBA sided with the wind developer, which had said that the state laws allow wind farms to produce up to 10dB more than ambient sound levels; the county had been suggesting that if the developer doesn’t conduct ambient noise studies before construction, they must assume ambient of 26dB.  The LUBA decision said that this requirement to choose whether or not to do an ambient study prior to construction did not appear in the state rules, leaving room for companies to show later that measurements of turbine noise levels exceeding 36dB were  made when the ambient was above 26dB.

Two recent articles in trade magazines caught me up on efforts taking place within the wind power industry to reduce the noise levels of wind turbines. While it’s great to know it’s on everyone’s mind, it also appears that so far, noise reductions are modest.

In the July 2011 issue of North American Windpower (back issues not available for online reading, sorry to say), one of the feature articles was “Turbine Manufacturers Focus on Reducing Noise Emissions.”  It included discussions with reps from most of the major turbine manufacturers, and was full of fascinating hints of ongoing research.  As the article noted:

As the so-called “low-hanging fruit” of land with good wind and transmission access gets used up and wind turbines move closer to residential areas, noise concerns are expected to become more prevalent, according to wind turbine manufacturers.

“It’s on the top of the minds for all manufacturers,” said Paul Thompson, commercial director of Mitsubishi’s wind turbine group, “we’re all doing things to reduce the amount of noise that’s generated.”  GE’s Henrik Stiesdel stressed that wind turbines do “have a noise impact.  The main remedy is to ensure that they are not sited to close to dwellings. If that’s not possible because you are in a densely populated area, then we have remedies where we control the power output when conditions are such that noise might be exceeding limits.” The article describes this system:

GE’s sound power management (SPM) works by optimizing control setting based on real-time wind conditions, according to Sean Fitzgerald. The SPM option can be configured for day and night modes, at angular intervals depending on the mode switching and based on wind turbine placement. “These applications enable the customer to specify the appropriate, desired sound emission characteristics by customizing the sound power curve to the precise requirements over the entire wind speed range,” Fitzgerald tells NAW.

Gamesa’s Miguel Angel Gonzalez-Posada notes that there’s a trend of having to keep noise as low as possible near populated areas, especially at night.

Read the rest of this entry »

The Roanoke County Board of Supervisors has adopted a wind energy policy that sits on the least-protective edges of current siting standards: a 60dB sound limit, and setbacks of 1000 feet from homes. Four of the five supervisors supported the proposal, saying it would protect residents; the 60dB limit was said to be comparable to sound along US 460, a four-lane federal highway in the area.

A fifth board member, representing the district where the only current wind farm proposal is sited, encouraged the board to hold off on setting absolute limits; Ed Elswick said the county should wait until it has a proposal and hire experts to weigh in “rather than grabbing numbers out of the air.” That didn’t stop him from tossing a number in the hat: he proposed that sound be limited to levels typical of rural areas, suggesting 30dB at the nearest property line.

UPDATE, 10/12/11: Elswick has asked the board to reconsider the 60dB limit; it will be on the agenda at a meeting in late October. Two board members said they knew they wouldn’t change their votes; one said he wanted to hear further discussion, and the fifth board member was not present when Elswick raised the issue again. And, 26 local residents have sued the Board of Supervisors, saying that the sudden shift from a 2600-foot setback proposal to the 1000-foot decision lacked proper notice of a public hearing, and was “clearly unreasonable, arbitrary or capricious.” UPDATE, 10/26/11: The Board of Supervisors voted to not reconsider their previous decision.

The area where 15-18 turbines are currently proposed is a section of hills about ten miles from Roanoke, a near-to-town rural enclave that has federal highways two to four miles in two directions, along with I-81 a few miles distant (see 2 mile scale at lower left, above). It appears that no existing ambient levels have been determined there, though it would not be surprising if some of the highways are faintly audible at the site.  There may well be homes in valleys, however, where current soundscape conditions are notably free of road noise, and which will now face next-to-the-highway noise levels from turbines on ridges nearby.

It is unclear at this point how many homes are close to the 1000-foot setback distance; these will be the places where the soundscape is likely to be most dramatically changed. A half-mile setback was proposed in a previous draft of the policy; this would have likely minimized the likelihood of major impacts on neighbors, though it may not have eliminated noise issues entirely. In areas such as this, it’s often hard to site wind farms without fairly relaxed noise and setback limits.  Here, as in many other towns and counties, board members apparently felt that it was more important to not exclude wind development than it was to maintain current soundscape conditions in this rural enclave.

A sprawling wind farm in northern New York state is the latest new installation to trigger push-back from neighbors complaining about excessive noise.  The Hardscrabble Wind Project is centered in Fairfield, just north of I-90 between Syracuse and Albany; its three-dozen turbines stretch across parts of three towns, covering an area of roughly ten miles by three miles.

A recent local press report summarizes the current situation: several nearby residents have complained of noise issues, leading the developer, Iberdrola, and the town of Fairfield to commission noise studies to determine what sound levels were occurring.  The Iberdrola study found that sound was generally in line with the predictions made during project planning, falling below the regulatory limit of 50dB, though in high winds some recordings came in above that with combined turbine and ambient wind noise.  The town study will take place this winter, when the leaves are off the trees.

UPDATE, 10/4/11: Good local article on the preparations for the new noise study, with a classic example of neighbors reacting differently to the sound, one saying the noise “is really bad, very hard to live with,” and another saying “to be honest with you, I don’t even notice them.”

A look at the sound assessment documents compiled as the project was being approved offers some hints as to why this project might trigger noise complaints; several factors compound the likelihood of issues here.  First is the town’s noise limit of 50dB for non-participating neighbors, which is on the very high end of regulatory limits for wind farms.  The sound assessment went through several versions as the project was revised and refined; a noise analysis from March 2009 lists 25 homes where the modeled noise levels were predicted to be between 45 and 50dB; 11 were hosting turbines and 14 were not. An apparently final revised noise analysis dated December 2009 (after some site adjustments to some turbines) does not list the affected homes, but includes very detailed sound contour maps, which show well over a hundred homes sitting in the 40-50dB zone, where it can be expected that a significant minority of residents will find the noise intrusive (based on experience at other wind farms in similar communities, and on the limited research data we have available; for more on this, see AEI’s 2010 NEWEEP presentation on community responses).  It all adds up to the classic conditions that have often led to problems in rural towns that are home to many residents who are not actively farming and ranching: too many homes receiving noise levels close to (relatively high) regulatory limits.

The final hint that there might be problems lies in the March noise assessments definition of existing ambient noise. This is often the key factor that is given too little attention in wind farm siting,

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A Japanese research effort that’s been around for a while has gotten a blast of media fame this week, claiming the potential to triple power generation by using a ring around the blade-swept disc that focuses wind past the blades, as well as, I think, capturing some of the energy off the blade tips.  Sounds great in a headline, but as with most new turbine design “breakthroughs,” this one is early in R&D: the field trial models are only 5kw, with two 100kw, 13m-diameter, models recently erected. Whether the design can scale up, or be constructed economically in large arrays of smaller units, remains to be seen.  The weight of the ring has to be a challenging design feature when it comes to actually building large versions of this in the real world. Nearly every efficiency-improvement approach also touts a reduction in noise output as one of the benefits.

The best coverage of the “Wind Lens” research appeared on Clean Technica; they included these links to the lab’s research page and a conference poster. For good measure, here’s a couple other new approaches to increasing turbine efficiency previously covered in Clean Technica, with equally uncertain futures.  More power to all these researchers, whether in university labs or backyards.  Just don’t assume that a catchy headline means the revolution is neigh.  (Being a dreamer, I remain quite fond of ongoing research in California that seeks to harness extra energy by mimicking fish schooling patterns with small vertical-axis turbines, as covered previously here.)

Apparently this proposal has little chance of proceeding, but in June the British House of Lords spent two hours discussing a bill that would establish a 2km setback provision for new wind farms.  Such a setback would leave little room for new wind farms in England, but many suitable sites would remain in Scotland.

The Parliament website has the full text of the debate, replete with the always-entertaining combination of formality and shouted “interventions” from dissenting members.  Go to this page and scroll down just a bit, past the prayer and a quick “dog control notice”; the first major topic is the wind farm bill, and discussion lasts from 10:17 until shortly after noon.

The German Federal Agency for Nature Conservation (BfN) is working with a consortium of offshore wind companies to find ways to reduce the noise created during construction of wind farms.  An article in Der Spiegel is a good introduction to the efforts:

“From the standpoint of environmental protection, it’s necessary to decrease noise pollution in marine ecosystems,” BfN acknowledges in the introduction of its recent report. The study looks to the guidelines set forth by the Federal Environment Agency (UBA), which suggest that noise outside of a 750 meter radius from the construction site should not exceed 160 decibels. Techniques like bubble curtains, according to the BfN report, can meet this standard.However Greenpeace takes issue with this value because it is based on single-sound exposure — and it takes much more than a single punch into the bed rock of the sea floor to install a wind turbine foundation.

Eight companies are working together to investigate noise-reduction techniques; this article summarizes their goals.  This “Permanent Joint Working Group” is co-hosting a conference in September along with German federal agencies; here’s a brief intro, and here’s the conference website (good luck with your online translation service!)

This is somewhat old news, but I just heard about this workshop (thanks to Kathy Hemenway), and it’s full of useful insights: in March, the Consensus Building Institute brought together 100 wind farm developers, environmentalists, state regulators, and technical experts, including proponents and opponents of wind energy, to spend three days discussing what works – and more importantly, what doesn’t work – as communities seek to make informed and effective decisions about wind farm siting.

The quick list of take-aways posted by organizer Larry Suskind on his blog include reminders that there are hundreds of wind farms in the US that can be instructive as we plan new ones, and that it’s unrealistic to expect everyone to get behind ANY project.  Several of his bullet points sound like things that could really help reduce the perceived lack of respect for community concerns that often colors local proceedings, and so reduce the fear and resistance that accompany many wind farm proposals:

• Don’t let wind developers proceed without discussing how turbine operations might have to be restricted to reduce the risk to wildlife and the annoyance to neighbors.
• Do promise to compensate anyone who lives near a proposed facility for any decline in property values that might occur. (It is possible to buy “property value insurance” to make 100% sure that no one suffers any loss of property value.)
• Do realize that everyone reacts differently to noise and visual impacts.

And, in his most far-reaching observation, Suskind stresses the need to “Avoid the dueling experts syndrome that is so common when cases go to court.”  From the outset, he says:

It’s very clear that the traditional “town meeting” or “hearings” approach to energy facility siting is useless. Nobody learns anything at raucous public meetings…..Professionally facilitated stakeholder engagement (involving representatives chosen by the stakeholder groups themselves) can create a level playing field in which informal problem-solving is possible. This all has to be completely open and accountable.

Interesting stuff! And here’s a long blog post from one of the participants, including links to most of the Powerpoints and a lot of audio from the three days.

Wind development in the promising borderlands region along the Scottish/English border has come to a standstill, due to very low intensity ground vibrations interfering with a key nuclear test ban monitoring station in Eskdalemur, Scotland.  The Ministry of Defence has been tracking the increasing seismic interference from wind farms in the region, and says that any more would push the wind turbine vibrations  to the point that their seismic monitoring array would no longer be able to reliably hear distant seismic anomalies.

According to an article in The Guardian, “the swishing blades of wind turbines cause vibrations in the ground that can be detected by the sophisticated monitoring equipment at Eskdalemuir. An expert study for the MoD concluded that although the station could cope with some seismic noise, increasing this beyond a certain level would be unacceptable. The limit has now been reached so the ministry is objecting to every new wind turbine within 50km of Eskdalemuir.”

An earlier 80km exclusion zone has been a flexible one, with a period during which the MoD only excluded wind development as close at 10km from the installation, with several wind farms built in the 50km zone (orange circle at right).  At this point, however, the MoD feels they have reached the limit of acceptable infrasonic interference.

One wind power company, REG, which recently had a planned development rejected due to MoD objections, reports that efforts are underway to find a technological fix that could reduce the subtle vibrations that are causing the issues. One idea is to hang weights like pendulums inside turbine towers to deaden the vibrations from the blades. The MoD promised it would reassess its opposition if there were a proven technological solution.

It must be stressed that the vibrations being discussed here are extremely small, far below what would be felt in a home.  We’re talking about a sensitivity that can pick up small seismic anomalies from around the world.  Nonetheless, even though the MoD’s concerns at 10-50km are about impacts far below thresholds that neighbors would notice, I do wonder whether dampening technology developed to address MoD concerns would also reduce some of the more localized vibrations.

We need to keep clear the distinction between pure vibration, transferred through the towers into the ground, and the infrasonic elements of the sound from wind off the blades; it’s unclear that the proposed pedulum-inside solution would affect the in-air infrasonics. For that matter, the press reports are fairly vague about the source of the troubling seismic interference, with that reference above to it being related to wind off the blades, which would, indeed, imply that the strong infrasonic component of wind turbine sound is the source of the problem.  Still, the MoD’s concerns about effects at 10km or 50km should not be taken to mean homes in these ranges are at risk.  However, this does make me wonder whether any other industrial developments (factories, especially) that produce strong infrasonic sound are an issue at distances as far as 50km; if not, it may offer an example of how wind turbines are a relatively unique acoustic presence in the landscape.

This is very interesting, though may get blown out of proportion: in April 2010 a District Environmental Officer submitted a memo to his Ontario Ministry of Environment superiors that offered detailed comments about the field realities he observed, in relation to the proposed Provincial wind farm siting regulations. These regulations currently guide Ontario siting, and call for at least a 550m setback, and sound levels at nearby residences of 40dB or less; the memo cites observations on the ground to recommend limits of under 35dB, and perhaps as low as 30dB.

What’s striking about Cameron Hall’s comments is that his concerns about the 40dB limit are largely similar to those of an increasing number of acousticians who have also been coming to a consensus that lower sound limits may be necessary in many rural locations. In particular, Hall noted that the regulatory 40dB limit should be adjusted downward 5dB due to the pulsing swish of turbine noise, and that it may be necessary to also factor in the acknowledged 3-5dB of error that can occur in sound modeling and the slightly variable sound output of the turbines. Combining these, Hall writes that “it appears reasonable to suggest the setback distances should be calculated using a sound level limit of 30 to 32 dBA at the receptor, instead of the 40dBA sound level limit.”

In addition, Hall stresses another factor often brought up by those trying to understand why 40-45dB turbine noise is stirring up so many complaints: the fact that rural soundscapes in his district are often as quiet at 20-25dB, and noise intrusions should be kept to less than 10dB over that; this leads Hall to similarly suggest Read the rest of this entry »

The island community of Vinalhaven, Maine, remains embroiled in a contentious wind farm noise controversy nearly two years after three turbines began operating there.  The nearby Camden Herald-Gazette recently provided a good, detailed overview of the latest rounds of the back-and-forth between nearby neighbors, the local electrical coop that buys the energy, and state regulators.

An escalating legal tussle has developed since the Fox Island Wind Neighbors paid for noise monitoring and submitted data to the state indicating that the turbines were at times exceeding their regulatory limit.  The most recent salvo is a complaint filed in state court charging that state Department of Environmental Protection commissioners have overstepped their authority by over-ruling staff recommendations on how to deal with the violations.  The neighbors charge that compliance recommendations were watered down, and, most recently, requirements that Fox Island Wind prove ongoing compliance were removed.

The complaint details the unfolding disagreements, beginning in April 2010, continuing through September 2010 when the state DEP officially reported that the turbines were out of compliance by a few decibels in some conditions. Since that time, the complaint charges that three successive DEP Commissioners have meddled in the compliance process, culminating most recently when, according to the petition, “Acting Commissioner Aho, over the objection of DEP professional staff, and in direct contradiction of the findings in the November determination of noncompliance letter, issued a compliance condition order.” The petitioners are asking the court to vacate Aho’s order and replace it with an order drafted by DEP staff, and to review the alleged instances of political intervention.

The article linked above contains extensive quotes from the complaint, as well as from Fox Island Wind, the local developer of the project.

Meanwhile, as part of ongoing efforts to seek innovative solutions short of curtailing operations, the local turbines are in the process of being modified by GE, their manufacturer.  Crews are applying serrations to the trailing edge of the blades; this experimental technique is designed to improve air flow off the blades, thereby reducing noise output by 2-4dB.  See this 2008 AEInews post about earlier research into such techniques.

Throughout the controversy, including in this article, Fox Island Wind has often returned to the idea that the ambient noise of wind in trees is a key factor in the higher recorded sound levels, while neighbors insist that the turbines are clearly heard through this ambient noise. In many ways, the Vinalhaven situation is a perfect example of one of the key, and often-overlooked, factors in wind farm noise debates: the regulatory limit is high enough that even when in compliance, turbines can be clearly the loudest thing in the local soundscape, triggering severe annoyance reactions and sleep disruption for nearby neighbors. While the legal sparring focuses on a 1-3dB violation of the operating standards (a difference in volume that is barely perceptible at best), the underlying fact is that even the allowed 45dB is too loud for many of those living within a half mile or so.

A couple of in-depth reports on communities roiling with wind farm controversies are currently viewable online.  Both seem to present a fairly balanced story, featuring locals struggling with noise, locals and consultants who see the problems as minimal and wind development as necessary and important, and some government officials trying to make sense of it all. My reaction to the first one, Against the Wind, is below; I’ve yet to complete the other, a much longer series from the UK entitled Blown Apart: Wind Farm Wars, which appears to consist of four hour-long segments.

From Australia comes an hour-long investigative report from Four Corners, a 60 Minutes style weekly TV program. The report, entitled Against the Wind, can be viewed here (transcript also viewable online). Both of the featured families who are negatively impacted come off as reasonable folks, not hot-headed complainers or people caught up in fears seeded from internet research. One of them is Noel Dean, a fairly well-known name among those tracking these issues from afar (on the internet, yes!), and the others are Carl and Samantha Stepnell.  Dean and the Stepwells both abandoned their homes due to noise and severe physiological reactions, though they return to work their farms. The Stepnell’s home is 900 meters (over a half mile) from the nearest turbine, with three others within 1200 meters (about three quarters of a mile); they weren’t affected right away, but after about six months began being affected. Though they tried to ignore it and live with it, the were soon being awoken most nights and having headaches and other stress responses.  The stories told by Dean and the Stepnells are familiar to many others within a kilometer or two of wind farms.

The show also includes a glimpse of some recording done at Dean’s home by Graeme Hood, where there was significant energy at lower frequencies, but not as much deep infrasound as Hood had suspected would be needed to account for some of the impacts.  There are clear statements of many of the also well-known responses from industry and pro-wind folks, about the lack of clear data on any negative impacts, as well as footage of an event held by a community group that includes provocative images of burning turbines and distressed speakers urging the whole industry to be “shut down, everywhere” due to health concerns.

While the content of the show is fairly representative of the two sides of the controversy, it slips some in places,

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A couple of articles in this month’s Wind Power Engineering caught my eye.  What follows is more speculative than what you normally find on AEInews, but with that in mind, I encourage you to check the articles out yourself.

Both articles address basic issues regarding wind turbines: the wakes they create downwind, and normal wear and tear of turbine blades.  Neither one considers noise impacts at all, and I don’t have the engineering background that might allow me to make truly informed extrapolations.  But both certainly seem to be worth bearing in mind as project planners and managers address possible noise issues.  The main thing I wonder is whether either of these factors might make turbines slightly louder than expected, or than modeled under more ideal assumptions.

The first article covers a topic we’ve covered here at AEInews before: ongoing research into the turbulent wakes that stretch out downwind from wind turbines:

Today’s massive wind turbines reach into a complicated part of the atmosphere, Julie Lundquist expalins. “If we can understand how gusts and rapid changes in wind direction affect turbine operations and how turbine wakes behave, we can improve design standards, increase efficiency, and reduce the cost of energy.”

The second article focuses on routine maintenance of wind turbine blades, and explains some of the normal wear and tear that needs to be attended to.  It seems likely that at least some blade imperfections would add extra noise, which is of course largely caused by the airflow coming off the blades.

Traditionally, less attention has been paid to the repair and upkeep of turbine blades versus other components. Instead, preventive maintenance programs have focused on the internal mechanics of turbines due to the predictability of their maintenance requirements. Typical preventive maintenance plans for internal components fall into 3, 6, and 12-month work schedules. By nature, blade repairs are more difficult to plan. Blade damage can arise in manufacturing, transportation, and tower construction and erection. However, maintenance issues more often occur in the field from leading-edge erosion, weather, and other factors. A lack of predictability and historical data complicates preventive maintenance for blades.

Commercial turbines can have tip speeds of over 200 miles per hour. At these speeds, rain drops can take on the impact of small stones, and blowing sand has the erosion power of a plasma cutter. Studies have shown blade roughness and accumulated debris on the blades can reduce wind turbine performance by 5 to 30%. Blades that aren’t working efficiently can also create vibration that contributes to gearbox failures.

Joshua Crayton, a contractor who provides blade maintenance services, notes that regular inspections are especially important in windy seasons and following lightning storms. “Operators and owners are inheriting their wind farm assets and the responsibility of maintaining blades that are no longer covered by the (manufacturer) warranty,” he says. “Like any business, wind farm owners and operators typically run a lean staff and may not have an experienced maintenance technician in-house. Partnering with a service company can help them design a long-term, post warranty, preventive maintenance plan.”According to Crayton, a maintenance plan should be initiated before the warranty period expires. “A thorough internal and external blade inspection should be scheduled in the warranty period,” he says. “Once owners and operators take over care of a wind farm, these inspections should take place every two years. Personnel can conduct simple ground inspections while on-site, but there is no substitution for a close, visual examination performed uptower.”

PLUS: Two other short articles may also be of interest: one on design concepts for a 20MW turbine (today’s big ones are 2MW), and the other a very positive development, a 36MW battery designed to stablize output to the grid from wind farms.