AEI lay summary of:
Resonate Acoustics.  Macarthur Wind Farm Infrasound & Low Frequency Noise: Operational Monitoring Results. 18 July 2013.  Author: Tom Evans.  Client: AGL Energy Limited.  Download report here.

A new report from Australia is being touted as the latest definitive proof that infrasound around wind farms is no louder than infrasound from wind and human activity in areas with no wind farms. While providing a relatively robust new set of data, the study design leaves some important questions raised by wind farm neighbors and other acousticians unanswered.

This may be the most comprehensive infrasound/low-frequency study released yet: it includes several days of measurements made prior to construction of the wind farm, along with at least ten days of measurements made when the wind farm was partly operational, and ten more days once the wind farm was fully operational.  Sound was measured down to 0.8Hz, lower than some similar studies.  Most importantly, sound was recorded inside the homes, which were1.8km (1.1mi) and 2.7km (2.7mi) from the nearest turbines, on opposite sides of the wind farm; at both homes, there were many more turbines at slightly greater distances than the closest ones.

At the more distant home, daytime infrasound levels prior to construction were commonly 60-70dBG, with a few peaks of 80-90dBG (grey circles below); these measurements capture the natural ambient infrasound levels caused by the wind itself, along with contributions from machinery and vehicles in the area (the threshold for human perception is about 95dBG for pure tones, perhaps lower for pulsing sounds).  The peaks were much lower at night than during the day, only reaching 70dB at the highest wind speeds.  With the wind farm operating (yellow diamonds below), the range of results was generally similar.  Note that the operational data is not all turbine noise; some periods will have peak sound levels caused by the same local ambient sounds captured in the pre-operational monitoring period.

(dBG weighting accentuates 10-30Hz, the threshold between audible low-frequency sound and infrasound, and includes 2Hz-70Hz)

At the closer home, a limited pre-operational monitoring period only captured wind from a couple of directions, so the report’s operational results only consider periods with these two wind directions, as well.  (An appendix includes the full dataset of the operational period, which closely resembles that of the more distant home shown above, though peak sounds remain below 80dBG). In the limited dataset, pre-operational levels were significantly lower, clustered between 40-60dBG.  After construction, the bulk of measurements were in the same range, though there was a clear increase in periods with measurements of 60-70db, with a few peaks up to 75dB.  The authors of the report suggest that some of these higher measurements appear to be due to a transient non-turbine source (one chunk of them all occurred in one short period during which wind speed and direction did not change), and much of the rest may reflect higher daytime wind-related sound, rather than turbine sound, since the limited pre-operational period did not capture much data at high wind speeds.  They also note that, regardless of the source, even these peaks were within the range recorded at the more distant site pre-operation, so they reflect sound “no greater than levels that occurred naturally in the local environment (prior to the) operation of the wind farm.”

A separate section of the report addresses audible low-frequency noise, using the dBA-lf metric (dBA weighting, applied only to sound from 10-160Hz), and also reported as linear (unweighted) results at each frequency band (down to 10Hz when compared to regulatory criteria, and to 0.8Hz in a series of charts of median levels in each frequency band).  Again, results showed compliance with regulatory thresholds, except for a few 10-minute periods (roughly 2% of the periods); the authors of the report consider it likely that most of these are extraneous sounds, or would be in compliance if found to be steady, rather than variable, sounds.

(Ed. note: It must be mentioned that the authors of the report are exceptionally diligent in suggesting plausible alternatives to turbine noise for each of the occasions where operational sounds appear to be higher than pre-operational; on-site human monitoring would allow at least some of these ambiguous time periods to be more definitively characterized.)

This report offers some good, solid new data, collected over a relatively long period of time (10 days or so, rather than a single day) with a decent range of wind directions and with raw data collected down to below 1Hz.  While affirming that infrasound remains well below the 95dBG human perceptual threshold and 85dBG regulatory threshold, and also generally below the frequency-band limits widely applied to low frequency noise (10-160Hz), a few limitations in the research design leave several key questions unexplored:

First, the houses used in the study were relatively far away from the wind farm.  While there are some noise complaints at the distances studied (especially in Australia and New Zealand), the vast majority of neighbor complaints occur when turbines are closer, from a quarter to half mile especially, and out to three-quarters of a mile (a bit over 1km) with some regularity.  This study takes the important step of recording inside sound levels, but with many complaints coming at half or quarter the distance of even the closer home here (and a tenth the distance of the further home), we are left without a clear idea of infrasound or low-frequency noise levels at such locations. This may be especially relevant to the low-frequency findings, since even at the greater distances, inside low frequency sound was much closer to regulatory limits than were infrasound levels.

Second, the primary data is presented as 10-minute average sound levels.  In an attempt to consider whether they were missing important shorter-term variation, the researchers also looked at 1-minute averages, and for part of the data, 10-second averages.  They found that the 10-second averages closely tracked the 10-minute averages, with a similar amount of variation.  However, several acousticians have suggest that the negative effects reported by some neighbors are caused by much shorter pulses of low-frequency or infrasound: investigations have centered on the roughly once-per-second blade-pass frequency, and on even more rapid fluctuations that can only be captured when filtering sound at at time frames of 10 milliseconds, matching the sensitivity of human hearing.  It’s very likely that the 1-second peaks would show higher peak levels than the 10-second averages and 10-minute averages; one such analysis found 1-second peaks of 5-8dB higher than 10-second averages, with variations of up to 30dBG or more around the average when measured at 10ms, leading to peaks 10-17dB higher than the ten-second average.  While regulatory criteria rely on longer averaging times, human responses to much shorter-term peaks, and/or to short and long-term variability, may well underlie many  of the more vehement complaints that occur even when turbines are meeting regulatory noise limits.  Investigating this possibility more widely would help settle what is becoming a central question in community responses to wind farms.

Finally, even ten days of monitoring may well not capture conditions that are particularly troublesome for neighbors.  No indication is offered as to whether the monitoring was scheduled with any consideration for “worst-case” noise conditions, especially times of high atmospheric turbulence, or seasons when complaints have been highest (operational monitoring took place in southern hemisphere summer and autumn).  The report notes just one two-day period when the resident at one of the homes noted that the noise seemed particularly bothersome (results those nights were generally clustered within the typical scatter of data, though on the high side of the range).

While it may appear to some that these final points are nit-picking attempts to find any small reason to ignore the overall findings of this study, I offer them not so much as critique, but rather as a nudge to researchers, to dig deep enough to more definitively address some of the particular qualities of wind turbine noise that are being hypothesized as contributors to community responses to turbines.  In particular, averaging times for noise analysis must be well below one second (eg 125ms, or one-eighth of a second) in order to capture the amplitude modulation that gives many turbines their distinctive pulsing or throbbing sound quality.  

This study does a good job at assessing the wind farm’s infrasound and low-frequency sounds against the regulatory criteria; however, with community complaints being common even around projects in compliance, there’s a need for research that can help clarify whether wind turbine sound does—or does not—have unusual qualities or variability patterns that existing regulatory standards are not designed to address.

Noise complaints around the Sheffield Wind facility in Vermont began soon after the turbines began turning; combined with complaints from other wind farms, the Vermont Department of Public Service initiated investigations.  This week, a report was released summarizing the results from three days of noise monitoring outside the home of a family that has been especially affected by turbine noise.  Unfortunately, the conditions on these days were not similar to those that cause the residents problems; and more generally, on none of the three days were investigators able to document the turbine sound levels (on one day there was virtually no wind and they weren’t operating; on the other two, wind was too strong to hear turbines, and not from a direction that brings turbine noise to the house).

As reported on VtDigger:

Chris Recchia, commissioner for the Vermont Public Service Department, said that while the noise testing may help his department better understand how to evaluate wind noise in the future, he cannot draw conclusions from it.  “The testing is not helpful in terms of determining wind noise,” he said. “It really is not particularly useful in making conclusions about the compliance of the turbines.”

“This was our first attempt at trying to do independent noise testing, but it brings up more issues than it probably answers,” he said. “One of them is having a standard inside someone’s house.” 

The acousticians on site found daylong average noise levels of 30dBA on the relatively windless day, and 45dBA and 47dBA on the windy days; at no time were the turbines audible through the wind, leading the investigators to conclude that the turbines’ contributions to these levels were lower than the state limit of 45dBA.  The inability to isolate turbine noise in their monitoring left them unable to predict the inside noise level, which by state regs should remain below 30dB; they had assumed they could capture outside turbine noise, so had not arranged to make recordings in the house itself.  However, as the report says:

…it should be noted that in conversations with the Therriens, the three-day measurement period was not representative of the worst-case noise conditions that they experience. They are most impacted by the wind turbine noise when the winds are from the east and the south, and their residence is directly downwind of the wind turbines. If measurements are to be made that demonstrate these worst-case noise conditions, it may be necessary to greatly extend the time of measurement period to catch the particular operating and atmospheric conditions that cause the level of annoyance claimed by the Therriens.

UPDATE, 7/15/13: The Therriens and Vermonters for a Clean Environment have raised questions about the reported power output on one of the two windy nights.  According to a letter filed with the PSB, conditions were actually similar to previous high-noise periods on one of the testing nights, but the power output charts in the noise monitoring report show surprisingly low power output during some high wind times in the wee hours of the 2nd day of testing. Luann Therrien noted, “Up now at 2am.  Imagine our surprise we are not being rocked out of the house by turbine whoosh and jet sound.  First time in a long time that we are hearing mostly normal wind sounds (during a time when the wind speed and direction were optimal for loud turbine noise).” It’s possible that the wind project was under some curtailment from local grid operators who didn’t need the power at that time; VCE wonders whether the wind farm operator knowingly feathered the blades to reduce sound during the testing, though a spokeman for First Wind said, “Of course, we don’t make any adjustments when testing is going on.” For more, see the VCE letter to the PSB.

Some larger issues are also spotlighted by this study.  Charts included in the report offer a clear representation of the variability in wind noise over the course of the day—the daylong average levels, especially on the windy days, were far exceeded for much of the day.  While in this case, the noise was wind, similar variability is commonly also found in wind turbine sound (often 5-10dB above a daylong average, and at times 15-20dB higher, though generally with lower peaks than this blustery day produced); daylong average figures, while useful in many ways, rarely reflect the actual noise experience of neighbors.

The difficulties encountered in this study highlight the need for noise monitoring—especially at homes with repeated complaints—to be planned with enough flexibility to be on site on days when weather forecasts predict the conditions that residents have stated to be the most troublesome, and to be sure turbines are operating at full power at times when conditions are ripe for issues.  As noted in the comment section of the VtDigger piece (which features a lively, respectful discussion), those who are upset about turbine noise rarely say the turbines are always a problem; rather, there are often certain conditions that are significantly worse. To thus spend limited resources doing sound studies at randomly chosen times is likely to be of little practical use. The more troublesome conditions may occur more, or less, commonly in different locations, and may easily be missed by any brief monitoring period, unless spot monitoring is carefully and flexibly planned.

It should be stressed that even if the difficult conditions occur a relatively small proportion of hours per month, they can still create a chronic, hard to live with experience.  For example, one study suggested peak turbine noise levels may occur as little as 4% of the hours in a year; but, doing the math on 4% of the time shows that this could mean 116 days—a third of the year—with peak sound for three hours a day, or 58 days—nearly two months worth of days—with peak sound for 6 hours;  for more on this, and turbine sound variability in general, see this recent AEI presentation. (Note that this analysis is looking only at generalized yearly variability in wind-speed-driven turbine sound levels and some propagation factors, and does not incorporate any turbulence-induced increases in turbine sound levels; thus the 4% number is illustrative only, and not meant to represent actual rates of troublesome noise at any particular location. Few studies have looked at the effects of air turbulence or turbine wakes on turbine source levels, and none that I know of have actually tracked long-term patterns of sound variability around wind farms.)

RELATED, 7/23/13: More extended noise monitoring at another Vermont wind farm on Lowell Mountain has found no violations of the 45dB limit, including at times when turbines were operating at full capacity.  Turbines were monitored continuously for two weeks in May and June, according to a local news report on the testing.  Two earlier monitoring periods found a total of four hours in which turbines exceeded the noise limits; Green Mountain Power says this was due to snow build-up, and new equipment will allow them to shut down turbines if that happens again; a hearing in early August will determine whether Green Mountain Power will be penalized for the violations.

Earlier this month, I arranged to visit the wind research teams at Sandia National Lab and the National Renewable Energy Lab’s National Wind Technology Center, both of which are relatively nearby here in the southern Rockies.  I’ve been following the work of many of these researchers for the past year or so—it was central to my 2012 Renewable Energy World conference paper and presentation on efforts to quiet turbines—and was very interested in learning more about their past, current, and future studies.  

In particular, the Sandia team has recently built a Scaled Wind Farm Testing (SWiFT) facility, at which they’ll be studying wake interactions between turbines, and they’ve long been on the forefront of developing new materials and experimental active systems to reduce load strains caused by inflow turbulence.  They’re also leading the development longer blades, which may have important noise implications. Their most exciting forward-looking project is a 5-year effort to re-activate development of vertical axis turbines, with the goal of moving toward 5-10MW scale vertical axis turbines for use offshore (this will be a 10-20 year project, if the first phase shows promise).  Meanwhile, at NREL’s NWTC, lots of research has looked at the pinpointing the sources of sound on turbine blades, as well as advanced modeling of sound propagation in various atmospheric conditions.  Researchers there have quantified the power-production trade-offs caused by wake interactions within wind farms, and are on the leading edge of new technology that might allow individual turbines to monitor incoming air flows and adapt their operations to minimize loads and noise.  All of this research has intrigued me, because of the likely role of wakes and atmospheric turbulence in wind turbine noise levels, and in creating some of the more intrusive sound qualities that neighbors find hard to live with.  My hope was to sit down with these researchers and learn more about their work, as well as draw on their experience to see whether they thought the turbulence factors they study to reduce stress on turbines may indeed also have an effect on the sounds.  

As it turns out, they were also intrigued by such a dialogue, and both labs asked me to present their teams with a seminar on what I’ve been learning about community responses to turbine sound.  Much of what I shared was new to them, and we had some great discussions.  One of the central take-aways from both teams was that very little research has really looked at the acoustic effects of inflow turbulence, and there was universal agreement that this is an important area for future study (as a start, the SWiFT facility will incorporate some acoustic measurements).  Many of them were especially interested in the varying sound quality of turbines, and the ways that this may trigger negative responses among neighbors; there was much speculation about the potential to identify the conditions that create the troublesome knocking, banging, thumping sounds, and perhaps adapt turbine operations to minimize or eliminate them.  As I’ve long found in my interactions with academic and agency researchers, there was an easy openness and curiosity in both rooms, with many questions tossed around, and an excitement about studies they hadn’t seen before. 

Read or download my presentation: The possible role of turbine, wake and shear effects on community response to wind farm noise  (This is the “director’s cut,” including a few slides deleted for length from the final version, along with some additional slides from the REW conference presentation that cover related topics) 

Community Response to Wind Farm Noise: The possible role of turbulence, shear, and wake effects by jimcummings

Planners have long recognized what they call a “demographic shift” in areas near new or expanded airports and highways: in the years after construction of the new noise source, some proportion of nearby residents move away, seeking a return of the quiet they desire.  Since about half the population is very noise tolerant, buyers who don’t mind the moderate noise are usually found. Sometimes homes must sell at a discount, and in other cases, the price isn’t significantly affected; rarely, homes with especially severe noise exposures cannot find a buyer at all.

An article in South Coast Today gives a sense of how this is playing out in Falmouth and Fairhaven, where dozens of families within a half mile or so of turbines have been struggling with noise.  As is often the case, the takeaways are ambiguous.  Two residents near the Fairhaven turbines are quoted, both of whom are reluctantly moving from their homes.  One, who’s been sleeping in his living room because the noise in the bedroom keeps him awake, has found a buyer who’s paying just 7% below his asking price.  The other, whose kids and their mom have already moved away because their 8-year old was having trouble sleeping, had his house on the market at a low-end price, and after “watching buyers come by, look at the turbines and drive away” for several months, he’s now hoping to find renters.  Likewise, a local realtor speaks of a house around a half mile from the turbines that’s been on the market for two years: “They ask about the noise, they ask about the flicker, and then they don’t put in an offer,” she says, noting that the asking price has dropped from $389,000 to $244,900.

In Falmouth, realtors speak about similar troubles finding buyers, with some homes being passed from realtor to realtor as they attempt to sell.  However, the director of Falmouth’s Assessor’s Office says that homes near the turbines have sold at “close to or more than” the assessed value.  At the end of last year, a couple that was one of the closest neighbors to the one privately-owned turbine in Falmouth abandoned the home they designed and built, and started over with a cheap fixer-upper; I have not heard whether it has been sold or not.

In the first town-wide vote on the question of what to do about noise issues around two town-owned turbines, Falmouth voters overwhelmingly defeated a measure that would have authorized the Selectmen to continue on their preferred path of dismantling the turbines.  The proposal carried a likely pricetag of about $800 per household, spread over ten years, largely to pay back loans and renewable energy credits that the town received in advance in order to buy and install the turbines.  The measure fell by a 2-1 margin, with about 40% of the town’s registered voters turning out.

Board of Selectmen Chairman Kevin Murphy said that the board will now begin looking at other ways to try to address the long-simmering dispute.  About 40 households have formally filed complaints, representing 15-20% of the homes within about a half mile. Since noise monitoring showed some violations of state noise limits, the two turbines do not run at night, so operate at a loss to the town, though they still produce carbon-free electricity for use at the town’s wastewater treatment plant.

For more on the Falmouth vote, see coverage in the Cape Cod Times and from the AP.
UPDATE, 5/25/13: Three neighbors respond to the vote in this local article.
UPDATE, 6/5/13: Neighbors emphasize that the vote was about funding the previous decision of the Selectmen to take the turbines down (not about whether the turbines should operate), and that the problems will need to be addressed by the incoming Board of Selectmen and/or the Board of Health.  They also say the state should step up with some financial help or forgiveness to lessen the burden on town taxpayers.
UPDATE, 7/5/13: The Board of Selectmen have begun discussing their options for resolving the turbine issue.  See local coverage of their first public discussion here and here. 

Across the bay in Fairhaven, the first results of noise testing were announced at a Board of Health meeting, marking a turning point not unlike one Falmouth encountered about a year ago.  Monitoring by the state Department of Environmental Protection has found that the two turbines in Fairhaven exceeded state noise limits in 5 of the 24 testing periods analyzed so far (more testing in varying wind conditions is ongoing).  All of the violations ranged from 0.7-1.5dB over the limit of 10dB above background ambient conditions.  Two to three decibels is considered the threshold of the human ear being able to hear an audible difference, so these noise levels are not perceptibly louder than sound just below the 10dB threshold; however, we once again see evidence that the 10dB-over-ambient standard is pushing the tolerance of neighbors.  As Fairhaven board of Selectman Chairman Charlie Murphy said, “Before, people didn’t believe the turbines were that loud at night, but now the study shows it,” adding that the results leave him more determined to “give our residents a good night’s sleep.”

As in Falmouth, where violations were also found in only some conditions and just over the limits, dozens of neighbors are complaining of lost sleep and other related health issues.  EPA standards developed in the 1970’s suggested that noise sources are fairly well tolerated when they remain within 5dB of existing ambient levels, and that at 10dB above ambient, “widespread complaints” are likely.  The detailed results from Fairhaven were not released, but the Falmouth report showed all locations exceeding 5dB, and most exceeding 7dB.  Some states still use 5-6dB thresholds, though many have moved to the 10dB used in Massachusetts, or refrain from the difficult task of regulating noise based on ambient conditions.  The Massachusetts measurement protocol has elements that may in part compensate for the larger 10dB threshold, and other elements that could counter that compensation: the standard compares the L90 sound level (quietest times) of ambient conditions with the absolute peak sound levels of noise from the turbines, rather than the average of each, which may somewhat increase the dB difference; however, the use of “slow” five-second time averaging, rather than “fast” one-second samples (closer to how the human ear perceives sound) likely results in lower peak measurements. Again, though, quibbling over exactly how the measurements take place can obscure the larger issue, which is that current standards appear to be insufficient to keep complaints to a minimum.

The three large wind farms currently operating in Vermont have spurred enough noise complaints to trigger an investigation by the state Department of Public Service.  DPS Commissioner Chris Recchia said “I want to get to the bottom of this….It’s not what was expected.”  Recchia suggested that he’s considering asking the Public Service Board to reconsider their existing noise standards.

Since last fall, 105 formal complaints have been filed, by 23 different individuals living near the Sheffield, Lowell, or Georgia Mountain wind projects.  Annette Smith of Vermonters for a Clean Environment is also collecting confidential complaints, some from people who have filed formal complaints, and some from neighbors who have felt it to be futile to complain to the turbine operators and/or state.  

The DPS is hiring a noise expert to analyze the complaints, and comparing them to quarterly noise measurements made near each wind project.  After this analysis, the DPS has three options, and could recommend one or more: enforce standards if they find violations, create a more effective system for operators to respond to complaints, or ask the PSB to change the noise standards if necessary.

See this recent local news article for more, including details of a recent bad night for neighbor Kevin McGrath, whose house is pictured above.

A month after Falmouth’s Board of Selectmen voted to recommend dismantling of the two town-owned wind turbines, a Town Meeting vote fell seven votes short of the two-thirds majority necessary to authorize borrowing money to do so.  A follow-up measure authorizing $100,000 to develop proposals for decommissioning will be discussed as the Town Meeting continues tonight; since that measure won’t require borrowing money, it will need a simple majority.  The Selectmen plan to put the question of decommissioning before the entire town during a May 21 town election. (In Falmouth the Town Meeting is a representative body of about 300 residents.)

UPDATE, 4/11/13: On the final night of Town Meeting, a 90 minute discussion resulted in a measure that will put the $100,000 question before the full town in the May 21 election, rather than authorizing that money to begin to be spent immediately; in addition, this money may only be spent if the town as a whole votes to dismantle the turbines. At its April 11 meeting, the Board of Selectmen agreed to put a binding referendum on the May 21 ballot, approving additional tax levies to cover deconstruction of the turbines.  Coverage of this discussion and vote is here.  Also, the town meeting in nearby Scituate voted down a non-binding citizens proposal to urge revocation of the local permits for a single turbine that has also spurred complaints from its nearby neighbors; coverage here and here.

Last week, the Massachusetts Clean Energy Center said that it would consider forgiving the town $2 million in Renewable Energy Credits already paid and due to be delivered in the future, but only if the turbines were not dismantled, and the town did not impose any noise restrictions more stringent than state regulations.  This represents a small part of the estimated $12-15 million total necessary for decommissioning; over $10 million of this is outstanding loans, which the town hopes will be reduced via debt forgiveness by the state for one turbine, and possible state financial assistance for the other.  In the recent vote, though, the Town Meeting was considering a measures that would authorize the town to spend up to $14 million, since state support is uncertain.  The proposed borrowing would raise average property taxes by $48 per year, or a total per household of about $800.

The two town-owned turbines had been projected to create a net revenue of several hundred thousand dollars a year, in electricity saved at the town Wastewater Treatment Plant, electricity sold on the open market, and Renewable Energy Credits.  However, for the past year, since state DEP noise monitoring found noise levels exceeding state limits in the nearby neighborhood at night, the turbines have been shut down at night, and so operating at a deficit of about $100,000 a year due to the significantly diminished output. This recent article in Cape Cod Times provides a history of the turbine project in Falmouth, the emergence of impacts among neighbors, and the town’s efforts to decide how to respond.

At the town meeting, local green energy advocates urged a “no” vote, saying that it would be more  cost-effective to buy houses from those most upset with the turbine noise, while two Selectmen spoke in favor of the measure, because of the current annual losses, the need to heal the split in the town, and the fact that a town Wind Turbine Options Process group that met for several months came to the conclusion that, among several final options, decommissioning was the best choice.  

If the May 21 town-wide vote agrees to dismantle the turbines, the matter of borrowing funds to complete that process will return to the Town Meeting at another of its biannual sessions.  Meanwhile, town officials will continue to develop plans to navigate the “considerable complexity” of arranging all the necessary financing, contract revisions, and special legislation that will be needed to complete the process.

A environmental planning Tribunal in Victoria, Australia recently completed 28 days of hearings about a proposed new wind farm above the Trawool Valley.  In a recent statement and preliminary report, the Tribunal noted that health effects were the central issue, and that the testimony presented left them still unable to make a clear determination about whether the wind farm will pose an undue impact on human well-being: “In summary the Tribunal has been made acutely conscious of the questions but finds itself in a less than satisfactory evidentiary vacuum regarding the answers.”

UPDATE, 11/27/13: The Tribunal has ruled that the wind farm can be built.  It will be the first new wind farm constructed since Victoria adopted a 2km setback standard.

The Tribunal notes that it found the evidence of health effects to be both consistent and convincing, though both the extent of the problem and the cause were far less clear. It also notes that many (though not all) of the health effects referred to in the literature occurred at distances of less than 2km, which is the statutory setback in effect in Victoria.  Getting more clarity on how common effects are beyond that distance appears to be at the heart of the Tribunal’s decision to postpone a decision for six months:

The Tribunal considers that the issue of health and wellbeing raises two distinct questions. The first question is whether there is a causal link between sound pressure emissions from wind turbines and adverse health effects on nearby residents. The link may be physiological or psychological. However, given that the respondents expressly disavow that the impact is psychological and that the so-called “nocebo effect” lacks any empirical basis, the inquiry in this case must be as to whether there is a physiological cause. In this regard Mr Cooper hypothesised that wind turbines may emit a particular low frequency “signature” that gives rise to the problem.

One difficulty facing the satisfactory resolution of this question is that there appears to be no overlap of expertise between the acousticians and the health experts. The acousticians can measure the noise but are unable to say what effect it has on human health. The health experts can identify the health issues but are unable to connect those issues with particular levels of noise or sound pressure. It is this that creates the need for interdisciplinary studies.

If the first question produces an affirmative answer, the second and equally important question is what is the incidence of health problems amongst the nearby residential population, and how does that incidence vary or attenuate with distance from the wind turbines. Obviously the problem must be given greater weight by decision makers if 50 per cent of the population surrounding a wind farm is affected rather than 5 per cent.

The full statement linked above (which also has a long section on noise annoyance and sound limits), and an excerpt containing the section on health and well-being, paint a pretty solid and concise picture of the Tribunal’s quandary.  The South Australian EPA is conducting a study around the Waterloo wind farm in the next couple of months that may help answer at least some of the questions, and the Tribunal is eagerly awaiting these results.  It has also invited both sides in the dispute to submit further information that contribute some of that interdisciplinary insight mentioned above.  

UPDATE, 10/23/13: The next round of evidence will be presented to the Tribunal, as requested, this week.

A surge of widely-publicized papers purporting to show that those complaining about wind farm noise are being unduly influenced by expectations of harm, or have personalities that are easily upset, may be fostering distrust among residents of Ontario who are randomly selected to participate in an upcoming large-scale survey funded by the provincial government and an ongoing 5-year study by University of Waterloo researchers.

This post, for example, notes that “mischaracterizations are coming out from all around,” and encourages residents to beware of any new surveys that appear to be asking questions about one’s overall quality of life or any annoyances other than wind farms.  The concern seems to be that general quality of life or attitudinal/psychological questions can contribute to the sorts of extreme claims that have filled the press recently, suggesting that “nocebo” type effects are the primary cause of health symptoms and annoyance complaints.  A detailed comment in the post includes a letter sent by one resident who returned a recent University of Waterloo survey without completing it, noting that “questions appear to be constructed in a manner that can be manipulated to achieve any desired result.” Here’s another site that similarly characterizes the UW survey as a political and wind industry sham.

All of these surveys, in order to be representative, need to have responses from a representative sample of both people being bothered and those who are not bothered.  Here, as in some previous research local efforts, distrust has grown to the point that those most affected may not participate.  While for many of those being kept awake or otherwise affected by nearby turbines, the question at hand appears very simple—the turbines are the issue, and they affect me—a useful survey will need to do more than simply ask about turbine health effects.  There are a lot of contributing factors, and it can be useful to consider many of them.  

While such surveys may be subject to misleading interpretations at times, the fact is that surveys and studies are always interpreted differently by those on opposite sides of the issue—where one side sees proof of their supposition, the other sees vague results, poorly designed data collection, or exaggerated significance.  It’s clear that both the idea that turbine noise has nothing to do with the problems being reported, and the idea that turbine noise is inevitably harmful for those living nearby, are overstating what studies and surveys have found. Still, such disputed studies provide raw data that can help quantify the extent of issues and become valuable sources of clear information for those on both sides of the issue, and especially for local decision-makers. 

In particular, if those most affected decline to participate in the Ontario studies, these surveys will come to conclusions that far fewer people are bothered by noise than are, in fact, affected.  This can’t be good for anyone.  Rather than fear the possible misinterpretations, it would be better to help assure that these surveys obtain results that reflect the actual extent of the noise problem.

UPDATE, 4/15/13: Some area residents are telling the University of Waterloo researchers that it’s already too late to measure pre-construction stress and other health markers.  This study is meant to provide a “before and after” picture of local sleep and overall well-being.  But, according to  an article in Niagara This Week, residents question whether it will do so:

“You’re not starting in the right place,” resident Debbie Hughes told Bigelow, during the public comment portion of Monday’s meeting. “We are already affected by the turbines. Our stress is already high.”

A dozen residents, all opposing wind turbines, shared similar messages. “It’s too late, two years too late,” said Helen Kzan, wearing an NRWC receptor 2418 bib. “I’ve been to the doctor. They told me to move.  My stress level has skyrocketed. My physician told me my stress will kill me before the wind turbines.”

While what the locals are calling “the pre-stress level” is likely already be elevated, it would still seem likely that the study could identify any trends in sleep disruption and more widespread stress that may be caused by the noise of the turbines once they’re built (at least, if those affected choose to respond to surveys). The whole situation highlights the ambiguities that exist in trying to determine the cause of any health effects that do occur.

AEI lay summary of:

• Simon Chapman, Alexis St. George, Karen Waller.  2013. Spatio-temporal differences in the history of health and noise complaints about Australian wind farms: evidence for the psychogenic, “communicated disease” hypothesis. Download this paper (pdf)
• Crichton, F., Dodd, G., Schmid, G., Gamble, G., & Petrie, K. J. (2013, March 11). Can Expectations Produce Symptoms From Infrasound Associated With Wind Turbines? Health Psychology. Advance online publication. doi: 10.1037/a0031760 Read/download this paper (Scribd)

Click here to download a 12p PDF version of this extended post 

If the detail in this post is more than you can tackle, I encourage you to take a look at the first several paragraphs through the brief assessments, then click through and scroll all the way down to the final few paragraphs, which look beyond these two particular studies and reflect on the health effects issue and its role in the larger debate over wind farm siting 

In Australia, the debate about wind farm siting standards has ramped up beyond what we’ve seen in the US and Canada.  Several states have adopted more precautionary setbacks (2km, with some options for closer siting), and this has spurred some pushback from wind energy advocates.  Meanwhile, the Waubra Foundation has become a central repository for information on negative impacts, and has released a series of reports and statements highlighting health effects and home abandonments, while calling for an even more precautionary 10km setback standard.

Recently, two reports were released in Australia that have garnered worldwide attention for their claim that health effects around wind farms are caused primarily by negative expectations promulgated via the web and local chapters of groups such as Waubra.  One of these is a formal study published in the journal Health Psychology by a team from the University of Aukland, and the other is the latest (and most comprehensive) paper from Simon Chapman, a University of Sydney Professor of Public Health and outspoken skeptic about wind farm health claims.  

I’ve long been concerned that the adamantly contradictory statements of both wind advocates and concerned citizens groups are likely to be inadvertently contributing to anxiety and stress among wind farm neighbors, which could well be a major contributor to many of the most widespread health effects (especially headaches and sleep troubles).  These new papers are investigating plausible psychological factors, and both studies add some useful new insights; however, similar to my assessment of a recent peer-reviewed article touted as proof of health effects, digging into these two papers reveals data that is far less clear-cut and absolute than the conclusions drawn by the researchers, and especially as reflected in the simplified popular press accounts of the studies. 

The short version of my assessment of these papers:
The Chapman paper gathers a wealth of information about complaint rates around all the wind farms in Australia, and taken at face value, makes an apparently convincing case for Chapman’s preferred hypothesis about the differences he finds: that the presence of local and national groups harping on possible health effects is the proximate cause of health complaints, and indeed, for the actual appearance of the symptoms themselves among wind farm neighbors.  But Chapman’s insistence that the negative influence of “anti wind farm groups” can totally explain away all the noise problems is ludicrous. His paper frames all his data through this one lens, and makes no effort to consider other possible contributors to the differences he finds in complaint levels. At the same time, his inclusion of existing public health research on the nocebo effect and studies of psychologically-mediated responses to perceived environmental threats is a welcome addition to our consideration of wind farm noise issues; still, as I begin to dig into the actual academic studies that he cites, they seem to be at best suggestive of modest contributing factors, rather than offering data that’s strong enough to be posited as the sole or primary explanations for most noise complaints.

For example, the Crichton paper finds that expectations of negative health effects can create a statistically significant increase in the number and severity of symptoms reported by study subjects exposed to infrasound (and to sham infrasound).  However, the actual data shows only moderate changes in reported health responses, especially in symptom severity, rather than a dramatic difference between the subjects primed with negative expectations and those who were given reassuring information prior to exposure to the sounds.  The average severity of symptoms, rated on a scale of 0-6, averaged 1.67 for the group primed to expect no health effects, and an only slightly higher 1.94-2.13 among those primed to expect negative impacts—a far cry from the intolerable responses being reported by some wind farm neighbors.

Despite the fact that these papers don’t contain a “smoking gun” that explains away negative health effects, as wind advocates may be claiming, their findings can be seen as a likely part of the story.  The small differences found in the Crichton study may be due to averaging over all participants; perhaps some individuals responded more dramatically than her data shows; a stronger effect on some individuals could be embedded in the similarly subtle yet statistically significant trends in the Nissenbaum study that found worse sleep and psychological health among those closer to wind farms.  And the Chapman paper reminds us that those reporting health effects remain a small minority, even in areas with substantial community outcry.  As AEI has often mentioned, even empathetic researchers tend to suggest that significant health effects occur in only 5-10% of the nearby population; as discussed below, a divide is emerging between those who feel that such small numbers reflect insignificant impacts, and those who feel that we can and should avoid or better minimize such effects by increasing setbacks.

A local example of health effects: While statistical or laboratory studies can provide valuable insights, they can also distance us from the actual experiences under consideration. In Falmouth, MA, dozens of turbine neighbors have had enough sleep and health issues that the town is considering removing two turbines.  A bit over 10% of those living within a half mile have filed formal complaints; in some directions, 25% or more have had problems.  This recent article features quotes from a couple of these neighbors (including one, Neil Anderson, who is a longtime renewable energy supporter), and from state and local wind advocates.

Click on through for a more complete summary of these papers, and AEI’s current reflections on the health effects controversies

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Ocean-based renewables are destined to be a huge piece of a future carbon-free energy system—tidal, wave, and offshore wind are all likely to become more technologically and economically viable over the coming decade or two. As these offshore renewables mature, they will reduce the current pressure to site wind farms in more populated areas closer to urban electricity load centers.

Watching the decade-long struggle in Massachusetts to build Cape Wind, the nation’s first offshore wind farm, researchers and state officials in Maine have chosen a different path: they decided to tackle the engineering challenges of building turbines that can float in deep water far offshore, rather than the social challenges of building wind farms in shallow water close to shore (which use fundamentally the same foundation designs as onshore turbines).  Floating deepwater turbines can take advantage of even stronger, more consistent winds than their nearshore counterparts; along most of the east coast, offshore wind is far more reliable than onshore locations.

After several years of planning, 2013 will see two floating turbine projects in the water off the Maine coast.  A one-eighth scale (57-foot tall) prototype will be tested in a relatively sheltered bay near Castine; the small model must be sited in waves that are proportionately smaller as well, to simulate how a larger unit will do with bigger offshore waves.  Meanwhile, Statoil will be installing 4 3-MW turbines two miles off the coast of Boothbay Harbor; this close-to-shore site will allow for closer monitoring and testing of the units’ durability.  Both projects are aiming toward the eventual construction of large-scale wind farms, likely using 6-8MW turbines, in waters far offshore, though likely not for another decade or so.  The Bangor Daily News puts the big dream in perspective: “to harness the Gulf of Maine’s winds by 2030, placing a full-scale wind farm of about 170 turbines, each taller than the Washington Monument, in the Gulf of Maine. That farm would bring 5 gigawatts, or the equivalent of about five nuclear power plants, of wind energy to Maine’s shore.”

UPDATE, 5/9/13: University of Maine researchers unveiled their 1/8 scale floating turbine foundation.  See article and video here.

UPDATE, 7/12/13: Late-session political maneuvering in the Maine state legislature has led Statoil to put a hold on its plans for floating offshore development in the state.  Governor Paul LaPage, a vocal critic of Statoil’s plans, vetoed an energy bill and in order to move it forward, demanded that an existing contract with Statoil be temporarily shelved to allow the University of Maine to file a bid as well.  LaPage and other fiscal conservatives have objected to the contract approved by the state PUC,  which pays Statoil a higher rate than other Maine electricity sources (the logic being that this small surcharge now will lay the groundwork for a new job base in the state as offshore industrial wind matures over the coming couple of decades).  The Statoil contract approved by the PUC uses up all the state incentives that have been approved for offshore wind in Maine.  It’s unclear whether the UMaine team wants to submit a bid; many see long-term cooperation between Statoil and UMaine researchers as the more fruitful way forward. An ideal scenario may find both projects getting contracts from the PUC, and thus be able to compete for some upcoming federal incentives for offshore wind development. In any case, the bill only holds up the commitment to Statoil for a few months, so the company’s sudden announcement of a hiatus may be more posturing than a fatal blow to Maine’s ambitious offshore vision. Local coverage here, here, and here.

MAJOR UPDATE, 11/7/13:  Since July, Statoil has definitively abandoned its project in Maine, citing political uncertainty that agreements will be upheld, and the University of Maine has released its plan, which aims to develop a 12MW pilot floating turbine project in the next few years, with the long-term goal of 500MW of deep water turbines by 2030, generating power at ten cents or less per kilowatt.  Here’s the latest.

The challenges for floating offshore wind are well-summarized in a recent article from SustainableBusiness.com:

Floating turbines cost less to install than conventional tower-based designs. They can be assembled onshore and then towed out to the installation site, eliminating the expensive and arduous process of building them out in the open ocean. On the flip side, the huge amount of steel needed to make turbines sturdy and heavy enough to withstand rough waves is too expensive. Engineers are working on solutions to get around that, such as intelligent systems that pump ballast water from one tank to the next as a way to stabilize turbines.

One thing that’s clear is the need for specialized turbine blades that can produce energy even as they rock and tilt on ocean waves. All that motion means more wear and tear and can also interfere with power generation. For now, all these designs are performing well, the question is more about which can be produced reliably at the lowest cost.

There has been some local resistance in Maine, especially about the power purchase agreements between Statoil and Central Maine Power for the energy from the pilot project near Boothbay Harbor, for which Maine’s electricity customers will be paying a premium.  State officials maintain that the small extra cost is a worthwhile investment in an offshore wind industry that could pay huge dividends in manufacturing and construction jobs in the years to come.  This is also a long-term investment in an electricity-generating future that can wean us from fossil fuels.  

While Maine’s electricity is already relatively climate-friendly, thanks to significant hydroelectric resources, the development of floating offshore wind in the Gulf of Maine could send lots of clean electricity to Boston and other New England cities.  Onshore wind in the Maine hills faces significant resistance as well, with locals feeling that the price paid by industrializing ridgetops and building new transmission corridors is not worth the modest benefit in green energy for neighboring states; the much smaller impacts of offshore wind may change that cost-benefit equation.   First, though, floating turbines will have to prove themselves durable, and the materials cost must be trimmed.  While that research is underway, offshore wind planners will need to insure that wind farm locations don’t interfere with key fishing habitat.

A new documentary from the CBC’s Doczone series, titled Windrush, takes a look at the widespread resistance to wind power in Ontario, which is largely based on noise and health impacts.  While the CBC video is only viewable in Canada, a regional organization opposing industrial wind has posted a version on YouTube (it’s 42 minutes long and ends a bit abruptly; it’s unclear whether it’s abbreviated, or simply missing the end credits).

This is a fairly balanced program, especially in highlighting the differences between building wind farms in the wide-open spaces of Alberta and the more densely populated rural areas of Ontario.  While it gives a lot of screen time to researchers and public officials who are studying the negative responses of many neighbors to nearby turbines, it’s useful and important to hear these sober and measured voices of concern.  The conventional wisdom, as reflected in the MOE health effects report, is also presented, though more as a context within which the program attempts to explore the persistent claims that living near turbines can be more difficult than these reassuring assessments suggest.

At times, the time constraints of the program lead to unfortunately abbreviated presentation of some key issues.  Grid integration issues are greatly simplified and distorted, leaving the impression that wind farms are inherently incapable of “playing nicely” with the rest of our energy generation system; the minute or two spent on this issue would have been better left on the cutting room floor, as it presents little more than a cartoon version of an important and over-hyped element of the story.  The treatment of low-frequency noise and infrasound is fleshed out a bit more, though some of the material would have benefitted from a bit more context, especially in areas where the science is still emerging and isn’t yet totally settled.  Finally, as local health official Hazel Lynn discusses the health effects being reported, she makes a comment that flits by so quickly that viewers may miss this crucial bit of context: while noting consistent symptoms being reported by people in many areas, Lynn stresses that these impacts are important even if they are only affecting 5-10% of the population that is more susceptible.  The rest of the program may leave the impression that severe impacts are being felt by most or all of the residents in these towns. (The question of what proportion of residents are negatively affected by turbine noise remains woefully under-studied.  Clearly there are many places where 20-50% of nearby residents dislike the turbines, most commonly due to some degree of sleep disruption, but this number is itself reflective of just a handful of actual surveys; we have no concrete sense of what proportion of people around most wind farms are either annoyed or experiencing chronic health effects.  Still, as Lynn suggests, for many, the question of “how many” is secondary to the need to address the fact that the noise does affect some.) 

Perhaps the most powerful element of the program is the aerial photography of wind farm areas, which give a compelling sense of the scale of the turbines as compared to the homes, as well as the vast landscape impacts, leaving many homes surrounded by turbines.  The segments filmed in Denmark are valuable as well; these reflect the growth of turbines from the 660kW machines common there, to the newer 3MW giants that are causing far more pushback, in both Canada and Denmark.  It also feels very valuable to hear and see some of the people who’ve been so widely cited about their concerns, including Lynn, Michael Nissenbaum, otologist Alec Salt, and acoustician Henrik Moller.  Too often, the basic human empathy and spirit of inquiry that fuels their work is obscured by the crassly dismissive near-vilification of these researchers by supporters of the industry (and also, to a lesser degree, by the hyperbole of some industrial wind opponents).  And, throughout the program, retired nurse Norma Schmidt, who eventually moved out of her house, is a calm and compelling voice for the experiences of neighbors who have been affected.  I heartily encourage anyone involved with wind farm issues to watch the film.  

For more, see the CBC Doczone’s Windrush web page, which includes a Director’s Statement, graphics, and several related stories.  And, here’s an article from The Observer about the film.

The Wisconsin Public Service Commission rejected the only large wind project currently in development in the state, citing noise concerns for homeowners in the vicinity.  The Highland Wind project sound models suggested that turbine sound would not meet the 45dB night time noise standard at about 20 homes. Some of the acousticians who submitted testimony in the Highland hearings suggested that limits of 40dB or less would be more appropriate; doubtless many more homes would be living with sound between that level and the current 45dB standard.  The recent collaborative sound study in Brown County was funded by the PSC in order to help understand the experience there before deciding on Highland’s application.  The developer of Highland, Emerging Energies, is likely to resubmit the application with adjustments to the turbine layout to keep all homes under 45dB.

UPDATE, 5/3/13:  The PSC has agreed to consider a revised plan from Emerging Energies, which may include night-time curtailments of turbines near the closest homes—apparently not routinely, but just when atmospheric conditions especially enhance sound propagation. 

Meanwhile, in the town of Heath, Massachusetts, the Planning Board and Renewable Energy Committee (REAC) has recommended that citizens approve a ban on industrial wind at the Town Meeting later this month.  Again, noise was a primary factor, thanks to the very quiet level of ambient sound in the deeply rural area; the REAC recommended a 2-mile buffer to maintain current ambient sound levels and preclude against any possible property value losses.  

The decision in Heath came on the same week that residents of nearby Monroe and Florida began speaking publicly about their experiences with the new noise from the Hoosac Wind project, which began operations in December.  Michael Fairneny says that at his house 3000 feet away, “My quiet, peaceful, serene world and home has been turned into a reeling of unending noise, annoyance and constant dealing with those in charge to help us.”  Six residents met the press to discuss their experiences, and say that at least 20 are struggling with noise issues. (A rough scan of a Google Earth image of the area, and referring to a map in the the 2003 permit application, suggest that around 150 homes are within about a mile of the turbines, with perhaps 80 within 3000 feet.)

Deepwater Wind, developers of a proposed 5-turbine wind farm off Block Island, Rhode Island, has agreed to refrain from pile driving for one month a year in order to minimize impacts on critically endangered North Atlantic right whales.  Pile driving, a key part of building the foundations for shallow-water offshore wind turbines, is the loudest aspect of offshore wind construction and operation.  Deepwater Wind, in consultation with the Conservation Law Foundation (which is deeply involved in right whale protection), agreed to suspend pile driving in April, the time of year when right whales are most commonly present in nearby waters.

Even before meetings began, facilitators of the multi-stakeholder group convened in Falmouth  to address widespread neighborhood complaints about noise from two town-owned turbines realized that the original goal of having group develop a consensus recommendation was too high a bar to aim for.  So, the process was dubbed the “Wind Turbines Options Analysis Process,” with a hope of being able to present two or three options to the Selectmen for consideration before this spring’s Town Meeting.

As it turns out, even that goal was elusive; in the end, the WTOP report summarizes four options, which generally reflect the initial stances of various stakeholder groups: take them down (the unwavering stance of the affected neighbors), run them at full power (the preference of the climate action groups in town and of those representing the town’s budgetary interests), or settle for one of two options involving shutting them down for all or part of the night (which satisfies neither the neighbors nor the climate or fiscal constituents).  In all three of the options that will cost the town money (removing turbines and replacing a third to half of their capacity with solar panels, running them full-time and compensating neighbors, and shutting them down for 12 hours each night), the WTOP recommended that the town seek funding from the state to support the initiatives.

UPDATE, 1/30/13: The Falmouth Board of Selectmen voted tonight to recommend that the two town-owned turbines be dismantled, and for the town to ask the state for funding to help cover the town’s debt for the turbines, and for the MassCEC to forgive the town for Renewable Energy Credits  previously purchased as part of the project financing.  The Selectmen will prepare a warrant article for the April Town Meeting, likely to be followed by a town-wide vote in May.

A few things stood out for me as I read through the 55-page report and some of the supporting materials (available at this link).

First and most striking, even among those advocating operating the turbines at full capacity it appears that the reality of the impacts on neighbors is generally acknowledged.  The report stresses that:

Although most of the discussion of acoustic measurement centered around whether, where, and how often the turbines exceeded DEP guidelines, most members of the WTOP acknowledged that operation within these guidelines would still not result in acceptance of the turbines by affected neighbors, since neighbors stated that compliance with the guidelines did not alleviate the health concerns they experienced.

In keeping with this understanding, the section of the report fleshing out the option of running the turbines at full capacity includes several measures meant to provide compensation for nearby neighbors; while brief, these options include purchasing (and reselling) homes, providing financial compensation that neighbors could use as they see fit (sound insulation or masking equipment, pay utility bills, etc.), and the possibility of the town offering a Property Value Guarantee.

A unique feature of the WTOP group was that it included two members whose charge, unlike all the other stakeholders, was to hold “multiple perspectives;” in essence, their task as individuals was to synthesize all the information, much as the group as a whole would ideally do.  With the group unable to find a synthesis of its own, the conclusions of these members are especially valuable.  

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In December, four acoustic consulting firms collaborated to study wind turbine noise at three Brown County, Wisconsin homes that had been abandoned by their owners after the nearby Shirley Wind Project began operations.  The study, organized by regional environmental group Clean Wisconsin and paid for by the state Public Regulatory Commission, will help inform the PRC’s consideration of a proposed new wind farm in the area.  

Two things stand out about this new study.  The first is the choice to bring together several acousticians who have previously been widely cited by opposite sides of the turbine siting debate. The study team included one firm  (Hessler and Associates) commonly hired to do sound assessments for wind developers, another (Rand Acoustics) that has become widely championed by concerned citizens groups because of its much more cautionary assessment of turbine noise, and a third (Schomer and Associates) whose work has often been in the middle ground, with particular papers being seized on by each side in the siting debate; the fourth firm (Channel Islands Acoustics) has worked much less on wind farm issues than the other three.  This diverse group of acousticians produced a 13-page consensus report (edited to 12 pages in the final version submitted to the PSC), along with an appendix report from each team, all of which focus on different aspects of the study that they found most compelling. 

The second virtue of this study is that it clearly documented, for the first time, specific sources of infrasound (sound at frequencies below 20Hz) and low-frequency noise (audible sound above about 20Hz) from turbines that are consistently measurable inside homes. The data they collected clearly showed peaks in the sound spectrum that correspond to the “blade passing frequency” (BPF) of just under 1Hz, or one pulse per second, and several harmonics of the BPF up to about 5Hz.  These pulses showed up both inside and outside the closest home, 1280 ft from the nearest turbine.  In addition, they measured a more modest infrasound and low-frequency peak at 15-30Hz, which reflects the natural resonance and flexibility of typical home construction; this peak may have been triggered by turbine sound or by wind or other outdoor sound sources. One of the acousticians, Rand, notes in his appendix a possibly corresponding pulse of outdoor sound in the 9-14Hz range that can be associated with inflow turbulence hitting turbines.  Still, the infrasound that was measured in this study, as in most other similar measurements of wind turbine noise, is at lower dB levels than what is typically considered perceptible by humans. (Ed. note: two emerging yet still limited bodies of work suggest that turbine infrasound may have rapid peaks that approach standard perceptual thresholds, and that our ears may respond physiologically to sounds at lower levels than are perceived; nothing in this Wisconsin study address these questions, though later analysis of the data may contribute to the study of short-term peaks.)

Since the study took place in homes that were abandoned by homeowners who all complained of debilitating health effects, including sleeplessness, nausea, and depression, part of the goal of the study was to see whether they could identify any possible acoustic triggers for these negative responses.  The authors collectively noted that “the issue is complex and relatively new” and concluded that this work “was extremely helpful and a good start to uncover the cause of such severe adverse impact reported at this site.”  

The consensus report, signed by all members of the team, introduces a new hypothesis, based on a US Navy study that found that vibrations can trigger nausea in pilots when in the frequency range of up to 0.5-0.9 Hz, with the peak “nauseogenicity” occurring at 0.2 Hz.  Of particular concern is that as turbine blades get longer, the BPF is being reduced; only the recent generation of turbines has dropped below 1Hz (thus perhaps helping to explain the recent surge of health complaints among a subset of turbine neighbors), and planned larger blades will drop close to that 0.2Hz range of maximum inducement of nausea.  While stressing that this is, as yet, a very preliminary supposition, especially since it involves a study based on physically vibrating the body, while turbine infrasound is a vibration of the air around a body, the authors still agreed that:

The four investigating firms are of the opinion that enough evidence and hypotheses have been given herein to classify LFN and infrasound as a serious issue, possibly affecting the future of the industry. It should be addressed beyond the present practice of showing that wind turbine levels are magnitudes below the threshold of hearing at low frequencies.

In particular, the research team agreed that a further literature search for studies related to vibration-induced nausea should take place (Paul Schomer is working on this), and that a “threshold of perception” test should be conducted, to see what proportion of residents are able to perceive the faint signals in either audible or infrasonic ranges.  Only one of the five acousticians, Rand, could detect sound at all residences; he also reported headache and/or nausea (it is also noted that he is the only one among the five researchers who suffers from motion sickness).

As often happens, the reaction to this study ranged from “this changes everything” to “this is nothing new,” with some saying it proves negative effects and others that it proves wind energy is safe.  For a run-down of the reactions, a brief look at each of the four appendices, and links to download the study, click on through… 

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Eastern Massachusetts continues to be a hotbed of both small-scale wind development and ongoing complaints in several towns.  Sixteen communities in the area now host one to four wind turbines (not all of which are full-sized industrial turbines); in five of these towns, complaints have been relatively numerous (a dozen to several dozen individuals).  Some of the turbines are owned by towns, generally to power a portion of town-owned facilities, and some are owned by businesses, for their own power, or by private wind developers.  

The Boston Globe published a series of articles this week that offer a good picture of the range of responses and opinions at this point in time:

• The main article features the full spectrum of views, including comments from neighbors, town officials, green energy advocates, a lawyer, a sound consultant, and a dispute resolution specialist (a slightly different version, abridged but with a couple different neighbor quotes, is also available)
• Another article covers a recent lawsuit by a couple in Scituate who live just 640 feet from a turbine there
• And a third article features the generally positive attitudes toward three turbines in Gloucester

RELATED: Falmouth’s First Abandoned Turbine House, a letter to the editor from a former neighbor of one of the Falmouth turbines, who’s cashed out her retirement savings and moved to another town

Timbertop Wind has asked the New Hampshire state Site Evaluation Committee (SEC) to assume jurisdiction over a proposed 5-turbine wind farm that straddles the town line between Temple and New Ipswich.  The SEC always has jurisdiction over projects of 30MW or more; the Timbertop project is only 15MW, so the SEC will decide later this winter whether to get involved.

The request came in part due to some differences between the Temple and New Ipswich siting regulations, though the primary concern noted by by Adam Cohen of Timbertop is the noise limits imposed by 2012 ordinances passed in both towns, which set a maximum noise level of 33dB on non-participating neighbors’ property.  “While the ordinance originally adopted in New Ipswich in 2010 was reasonable, the ordinances as adopted in New Ipswich and Temple in 2012 impose substantive requirements inconsistent with SEC precedent and state law,” Timbertop’s recent application to the SEC states.

In some other rural towns, noise complaints become more common as sound levels top 35dB, with sound levels of 40-45dB creating significant community annoyance.  The 33dB limit appears to be an attempt to greatly minimize the chance of serious noise issues for any neighbors, though turbines may still be slightly audible on some nights; see this recent post on noise studies in Woodstock, Maine, with noise levels at about what would be allowed under this ordinance.  

New Ipswich Planning Board Vice-Chair Liz Freeman said hat the board felt that it was the right level for a rural town like New Ipswich. “The Planning Board did not think it would be prohibitive and we did not think it was unreasonable,” she said. “It was based on recommendations from consultants with many years of experience on community noise issues.”  The wind ordinances were adopted with large majorities in both towns; Ed Decker, a New Ipswich Planning Board member, stresses that “The will of the people of New Ipswich was made clear by their votes, and it’s inappropriate for the state to override the people of New Ipswich.” 

See this detailed article in the Monadnock Ledger-Transcript for more.

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.

An Australian Senate Committee has recommended against passage of a proposed bill that would define excessive noise for wind farms as 10dBA above ambient, and suspend operations of wind farms failing to meet that standard.  In extensive submitted statements and published testimony, the Committee heard from a wide range of witnesses from Australia, the UK, the US, and Canada, including many names familiar to those following the wind farm noise issue.

The final report is also rather extensive; among the key reasons for recommending against passage was the perception that in Australia’s key wind farm areas, current regulations should be sufficient; in rural areas of New South Wales, South Australia, and Western Australia, noise limits are already 35dBA in quiet conditions.  Yet noise complaints continue to be widespread, though wind proponents and opponents disagree on how many are bothered; the Committee noted that distrust has led many people with problems to not lodge formal complaints with wind companies or regulatory authorities.  The bad blood goes both ways: wind company representatives reported that their attempts to meet with a physician reporting problems have been repeatedly rebuffed, while acousticians studying responses in some problem areas have found it impossible to obtain turbine operations data that would allow them to investigate correlations between operations and their measurements. A provision in the bill to require noise, weather, wind, and power data from wind farms to be made available online was met with strong resistance from wind companies, who felt it was an onerous requirement, and suggested that power data on specific turbines and wind could be “reverse engineered” by competitors and undermine their future project planning; the Committee recommended that such data be made available to regulatory authorities, rather than publicly (though in recommending the bill be not passed, it’s uncertain how or whether the full Senate might take up this point).  Another factor mentioned in the final report is that proponents of the bill presented testimony that suggested to the committee that there was disagreement about whether the proposed 10dBA over ambient limit was the best choice; indeed, some suggested that 5dBA over ambient would be more sensible, and others suggested lower dB limits, especially at night.  

While the focus of the bill itself was audible noise, some of the testimony addressed health effects and infrasound questions; on this point, the committee seemed to be especially interested in a presumed “nocebo” effect, by which an expectation of harm can lead to some proportion of people experiencing harmful effects.  While widespread reports of health effects was a driving factor among Committee members pushing for this bill, the final report suggests that some of the letters submitted, describing a wide range of symptoms, did not suggest any simple cause and effect.  The Committee seemed especially concerned by dozens of letters from areas where wind farms are not yet operating expressing fears about health effects should wind farms be built near them. The final report quotes a study on nocebo and infrasound which will be published next year.  Nocebo has been suggested as an explanation for clusters of health complaints around some wind farms; while the concept has been around for many years in relation to other sources of community concerns, it’s unclear how deeply it has been investigated.  Several witnesses pointed out that any such effect, even if it may apply to some individuals, should not be considered a primary factor when there are viable pathways by which audible sound can cause the observed responses, in particular in relation to sleep disruption by audible noise.  At the end of the Committee’s report, five Senators point out that the ongoing literature review being undertaken by the National Health and Medical Research Council does not fulfill the call by an 2011 Senate report, The Social and Economic Impact of Rural Wind Farms, for the Australian government to fund new epidemiological studies on wind farms and human health. 

Also of note is this excerpt:

The committee wishes to emphasise that it does not doubt that the symptoms are real. It also does not doubt that some people may be affected by audible noise. It is concerned, as Dr Tait from Doctors for the Environment Australia expressed, that the discussion about a purported wind turbine syndrome is hampering progress on the issue:
“Part of the problem, I think, of going around and promoting a wind turbine syndrome and going into communities and getting people scared about wind turbines is that it has muddied the water and it is distracting us from actually dealing with those small groups of people who have got a legitimate problem and do need us to be having some sort of debate about how we as a society work to help them with the issues that they are experiencing.”

The Committee’s records contain a wealth of documentation and perspectives well worth perusing.  The first link above takes you to the Committee’s page on the bill, where you can access a list (with PDF links) of all documents submitted to the committee by witnesses and the general public, as well as a transcript of the Committee’s hearings and testimony made there.

Researchers from Woods Hole Oceanographic Institute have begun a 2-3 year project that will monitor the soundscape at the Cape Wind site before, during, and after construction of the planned 130 wind turbines.  This is the first time such a long-term acoustic monitoring study has taken place at an offshore wind site.  

“We want to evaluate the importance of this kind of research for future offshore wind farm development, which is a rapidly growing field of interest in the U.S.,” Aran Mooney said. He and his colleagues are outlining a methodology for how acoustic monitoring may occur in other wind farm construction. Mooney said, “That will be valuable for industry, policymakers, and the public.”

Two kinds of acoustic recorders are being used: one records the full range of frequencies continuously for a week at a time; the other samples one minute of sound every ten minutes for 2-3 months, at frequencies up to 40kHz (thus missing echolocation clicks but capturing most other vocalizations of interest). “So we’re making the best of both worlds, putting one device out to get a really in-depth look for one week, and then we continue with the other device to get a sampling period of several months, then we replace both,” Mooney said.

During wind farm construction, pile driving will add significantly to existing human noise in the area; at European wind farm sites, some species tend to move  as far as 20km away during construction.  During operation of the wind farm, noise is not expected to be audible at distances more than a few tens or hundreds of yards, but this study will help to quantify exactly what frequencies are propagating into the waters.

Mooney would like to see the project also contribute to a growing research focus on using sounds to monitor overall environmental health of various habitats.  “Animals make sounds when they attract mates or reproduce, and you can track those activities just by listening,” Mooney said. “What I’d love to do with this project is to look at biological diversity. In a nice healthy habitat, you have a spectrum of sounds: low-frequency sounds of fish, then invertebrates a little bit higher, and then the seals and the dolphins.” The soundscape of an undersea area under an environmental stress would sound different; the impacts could be assessed by listening to what’s missing, for example.

For more on the project, see this page on the WHOI website, which also includes recordings of more than a dozen species of ocean creatures.

At long last, I’ve completed this year’s overview of science and policy developments on wind farm noise issues.  It features over 50 pages of new material, along with about the same in Appendices consisting of three research summaries I wrote earlier in the year.  You can download a pdf version of Wind Farm Noise 2012 here. 

AEI’s three Wind Farm Noise annual reports go into depth on different topics, and they complement each other quite well, though each one clearly engages the issues with more detail and reflects a more nuanced appreciation of the topic than the ones that came before. You can access all three, and AEI’s other publications on the issue, on our Wind Farm Noise Resources page.

But today, this is the one you should take a look at! AEI Wind Farm Noise 2012: Science and policy overview

I just came across a comment that seems to me to cut right to the heart of the question of rural communities where wind farm noise is an issue. This particular comment is another of several made public after the controversial disbanding of a wind farm noise technical work group that appeared poised to recommend tougher siting standards; see this earlier AEI post for that story.  But it hardly matters who made the comment below, or in what particular context, because it really distills the fundamental point of contention:

“We know that a significant number of persons are annoyed by wind farms. . . . I understand that many people live or move to rural areas for the country views and quiet. But individuals do not have rights to quiet or nice views.”

(For the record, the comment is in a letter from a former manager of the state renewable energy program, to an incoming manger.)

The argument is often made that turbine noise is far less intrusive than what city dwellers live with all the time, or that wind farms are not as loud as tractors, trucks, snowmobiles, or other mainstays of rural life.  These both skirt the central question, which is whether people, or communities, in rural areas can be justified in their complaints about noise, or in adopting ordinances that require significantly lower noise levels than the industry is used to (or perhaps even lower noise limits for turbines than what is accepted in noise from the everyday activities of rural life).

Many of the towns and counties that have recently established larger setbacks or lower sound limits are attempting to protect their residents’ rights to the rural quality of life and sense of place that they live there to enjoy.  The most extreme of these have setbacks large enough (2 miles) or noise limits quiet enough (as low as 25dB at night) to effectively offer absolute protection to existing peace and quiet; in so doing, they may also be effectively banning industrial wind development (though allowing for easements to build closer to willing neighbors may offer a way forward in towns where there aren’t large enough areas of open space to accommodate such standards).  

This is something that is likely to be played out in court, as wind developers, and at times residents wishing to lease their land to developers, have claimed that these strict rules represent illegal “takings.”  This week, the town of Peru, Maine, became the latest to adopt a strict wind ordinance, and the threat of such a legal challenge was a major point of contention as the planning board and Board of Selectmen discussed the proposal.  (The ordinance passed 585-30.  It calls for a 1.5 mile setback to property lines, noise limits of 35dBA during the day and 25dBA at night, and permanent sound monitoring after construction to assure compliance.) 

Kingston, MA, is the fourth town in the area to experience widespread public complaints about noise from small wind farms.  As in Falmouth, Fairhaven, and Scituate, town officials have begun holding hearings to hear from affected residents.  On Monday, the Kingston Board of Health voted to consult with the town’s attorney, to explore what options may be available to them.  There are two privately-owned wind facilities in town; the discussion this week centered on a single turbine owned by Independence Wind, while previous controversy has swirled around three turbines on land owned by Mary O’Donnell.  See the Boston Globe article for full details on the meeting; here are some highlights:

Kially Ruiz, co-owner of the Independence turbine, which began operating in May, said that he would not change the turbine’s operations unless there is proof it’s out of compliance with state noise limits; O’Donnell concurred, saying “Everyone in the room Monday knows all my turbines are well within the limits for noise.”  As a result of previous complaints, the Massachusetts Clean Energy Center is scheduled to hire a consultant to do sound measurements this winter, with results by spring.  This may well turn out to be another project in which turbines operating within legal sound limits still cause noise problems.  Such experiences have spurred some community groups and acousticians to recommend lower noise limits in areas close to many homes.

Ruiz insisted that his turbine is basically inaudible in surrounding neighborhoods, which have a highway, train station, and wastewater treatment plant in the area. “I think the neighbors are hearing a lot of things.  It’s just not the turbine.”  But Board of Health member Daniel Sapir begged to differ: “I went to the Reillys’ home at midnight, and I heard the whoosh,” he said. “You may say it’s not physically possible, but it’s happening. It’s real.”

Neighbor Doreen Reilly spoke of sleepless nights when that whoosh permeates the house, and said their lives “have been turned upside down. This has caused more anxiety than I have ever experienced. Our peace has been stolen from us. . . . We want our lives back.”

As the sun moves north along the horizon, shadow flicker has become an issue for her and others; they asked the health board to order the turbines to be shut down at night and for the hour or so a day when flicker occurs at nearby homes.  Of the flicker, she said “It causes headaches….It’s in every room of my house, and it makes you want to flee your home.”  

It’s not just sleep and peace that affected. Sapir, the Board member, experienced a dire impact that cannot be so easily brushed aside: late-afternoon flicker ruining a Patriots game: “It was so annoying I couldn’t enjoy the game,” he said. “The poor dog was cowering in the bathroom.”

AEI lay summary:
Nissenbaum, Aramini, Hanning. Effects of industrial wind turbine noise on sleep and health.  Noise & Health, September-October 2012, Volume 14:60, 237-43  Online access

A paper recently published in the journal Noise & Health is getting a fair amount of notice in the media; this article from The Telegraph is perhaps the most detailed coverage, noting that “the findings provide the clearest evidence yet to support long-standing complaints from people living near turbines that the sound from their rotating blades disrupts sleep patterns and causes stress-related conditions.”  This article from Ontario includes comments from co-author Jeffery Aramini and Canadian government and wind industry spokespeople.

SEE UPDATE AT BOTTOM OF POST re: Critique of this study contracted by AWEA/CanWEA and released on November 14. 

The recent paper is the formal published version of research previously presented at a 2011 conference, and summarized by AEI earlier this year.  The study employed three widely-used health questionnaires – Pittsburgh Sleep Quality Index (PSQI) to assess sleep quality, Epworth Sleepiness Score (ESS) to assess daytime alertness, and the SF36 for general mental and physical health – to compare sleep and health among 38 people living within 4600 feet of two wind farms in Maine to that of 41 people living in the same areas, but 2-4 miles from turbines. The authors conclude that “the levels of sleep disruption and the daytime consequences of increased sleepiness, together with the impairment of mental health, strongly suggest that the noise from industrial wind turbines results in similar health impacts as other causes of excessive environmental noise….Industrial wind turbine noise is more annoying than road, rail and aircraft noise, for the same sound pressure, presumably due to its impulsive character. This has led to an underestimation of the potential for adverse health effects of industrial wind turbines.”

The paper is being hailed as solid peer-reviewed proof of sleep and health effects of living near wind farms, though its findings appear less dramatic than the reporting.  It certainly does add some important, solid data that will be helpful in quantifying what have been largely anecdotal complaints and case reports.  A similarly rigorous survey in New Zealand, using a related WHO health-related quality of life questionnaire, was published in Noise & Health last year by Daniel Shepherd (also included in the AEI summary noted above).

While the new study found average sleep impairment and daytime sleepiness to be higher among those living closer to turbines, and the average “Mental Component Score” of the health assessment being lower among turbine neighbors, the data shows moderate trend lines, rather than dramatic differences.  Below is the data for the PSQI (lower scores reflect better sleep):

As you can see, there is a wide scatter of sleep quality – from the top to bottom of the scale – both among turbine neighbors and those living far from turbines.  This dramatic individual variability is, I’m sure, typical of the population in general, and so any trend line at all is a finding of note.  Still, there appears to be little indication that sleep quality is strikingly worse among neighbors, with the difference being apparent as a modest shift in the average.

The impact on sleep was most significant on those living closest (within 750 meters/2460 feet), where the average PSQI was 8.7, as compared to a PSQI of 5.6 among those living the farthest (over 5300m/3.3miles); there was a much smaller difference between the two middle groups (average PSQI of 7.0 at a 2500-4600 feet versus 6.6 at 2-3 miles). More striking perhaps is that 78% of the nearest neighbors, and 66% of the entire neighbor group, had a PSQI above 5, considered a threshold of concern, as compared to just 44% of those living over 2 miles from turbines (because of the wide scatter, the overall 66/44 difference was not statistically significant).  Even more notable may be that 12 (32%) of those within a mile had scores of 10 or more, as compared to only 6 (15%) of those over 2 miles.

Sleep disruption is widely considered a primary precursor for stress and other health effects, including headaches, emotional instability, difficulty concentrating, and possibly higher blood pressure. While this study did not find that those living closer to turbines have any notable difference in the Physical Component Scores (which includes pain, vitality, and physical function), they did find a reduction in the Mental Component Score, which assesses social functioning and emotional problems. As you can see below, while again the trend line shows a modest shift in the average scores, here the distribution of scores is quite dramatically shifted among those living closer:

The overall average MCS was 42 among turbine neighbors, and 53 among those living at a distance; both lie well within the 35-60 range that is considered typical of most people.  Those with scores below 30 are at significantly increased risk of clinical depression and need of mental health care; as you can see, the likelihood of this is much higher among those living closer to turbines.  We might note as well, though, that there is a solid cluster of turbine neighbors with high MCS scores, which reminds us that negative effects are far from universal. Still, just half as many people closer to turbines score over 60, the point considered a threshold of extremely solid mental health; similarly, only 7 (18%) of neighbors score over 55, as compared to 20 (49%) of more distant residents.

This study is an important step forward in our assessment of sleep and health effects around wind turbines.  It’s a stretch to tout the results as “proof of health effects,” as some of the press coverage implies, as the results don’t show dramatic or inevitable effects on sleep, and in fact no difference in overall physical health. However, the study provides quantitative confirmation that living near turbines can have measurable effects, and lays the groundwork for follow up studies.   As the authors note in their conclusion, this kind of study needs to be replicated more widely to prove causation, and “further research is needed to determine at what distances risks become negligible, as well as to better estimate the proportion of the population suffering from adverse effects at a given distance.”  Here’s hoping that studies like this and Shepherd’s will indeed spur continued research that moves our body of knowledge forward.

And one more finding of note: Among people living 2400-4600 feet (.45-.87 miles)from turbines, 35% said their sleep is worse at home than it is when they go away from the turbines.  But twice as many, 70%, said they wish they could move away from the area (78% of those living closer than 2400 feet would also like to leave their homes).  This is yet another reminder (as confirmed by the Shepherd study) that severe impacts on quality of life and sense of place are often much more common than are health effects.  (In addition to the intrusion on rural sense of home and place for many, impairment of rural quality of life could well trigger to the stress that may underlie some of the health effects.)  While it’s important to keep digging to clarify the extent and mechanisms of sleep and health effects, we shouldn’t lose sight of the larger, and in some ways more fundamental, questions about rural quality of life.

UPDATE, 11/16/12: Well, that didn’t take long. AWEA and CanWEA (the US and Canadian wind industry trade associations) commissioned an Ontario environmental sciences firm to  review the Nissenbaum et al study; the authors critique the methods and findings as reported.  You can see the critique here, or download a version with my comments (some of which agree with the critique, and some of which question whether technical issues really reflect shortcomings in practice). After years of stressing that there’s no data to suggest a relationship between wind farms and sleep or health effects, it seems important to the industry to shoot down the under-funded research that’s taking place where community response has been notable.  While it’s certainly valid to point out shortcomings in any research that’s out there, the same degree of diligence is rarely applied toward pointing out the limitations in the studies being cited as indications that health effects are no great concern.  This rapid critique is an example of the current internet-driven trend toward waging science by press release (again, not without some justification, since this study is being widely touted as “proof” by anti-wind activists). More useful would be the funding of solid epidemiological studies of health and sleep around operating wind farms, including some where complaints are common and some where complaints are rare.