Gar Lipow over at Grist has a quite detailed post today that looks at the promise of various proposed “Flying Energy Generators:”  tethered kite- or plane-like flying platforms for wind generation, able to tap into orders-of-magnitude more available wind energy than ground-based towers.  The piece addresses questions and concerns that are sure to arise about such a “pie in the sky” idea, and concludes that several designs that have completed a proof of concept phase are ready and enticing targets for truly modest government or venture funding to quarter and full scale commercial prototypes.  Links to companies working on several of the most promising approaches will really whet your appetite for more. Well worth a look!
More Than Pie in the Sky: Flying Energy Generators, Maybe the Next Big Thing

Two pieces of wind farm noise news out of Australia this week, both of which address health concerns.  Residents near the Waubra wind farm in Victoria, which began operating in February 2009, have been affected by the noise, some to the point where they’ve moved away.  A recent report by the federal government health office came to the familiar conclusion that there is no “direct, causal” link between wind farm noise and health effect, but as is common in these reports, little attention was directed toward looking at indirect impacts of sleep disruption or annoyance, and the authors of the report did not meet with any of the people who have experienced changes in their health after wind farms became operational.

In response, a Melbourne Senator has called for further inquiry. Senator Steve Fielding noted that ”I think it’s only fair that if a cluster of symptoms arise in a local population at approximately the same time we owe it to the people to take a closer look,” said Senator Steve Fielding. ”We all want to live in a clean environment, but we need to make sure it’s not at the cost of the local population who have to live near wind farms. It may be the case that we need to set out guidelines as to how close wind farms can be built to someone’s home, but I wouldn’t want to pre-empt any Senate inquiry.”

Meanwhile, one of the residents who had to move from his house, Noel Dean, commissioned a sound assessment by an independent acoustical engineer, Robert Thorne.  Thorne has submitted his findings to several regulatory agencies in recent months; there has been no significant challenge to his findings from wind farm developers, though he has responded to some specific critiques in his final report, which was just released.  Thorne’s report includes detailed sound measurements taken at the Dean residence; the results largely affirm that infrasound is well below audible levels, while also showing that the turbine sound spectrum (how loud the turbine is at each frequency) is often weighted toward lower-frequency audible and inaudible infrasound frequencies.  He finds a strong pulsing character to the noise, and notes the many meteorological factors that contribute to variability in actual sound levels that are not fully captured by current sound models. The report also contains a section assessing health effects, with good reference to other studies; his conclusion is that “Adverse health effects such as sleep disturbance, anxiety, stress and headaches are, in my view, a health nuisance.” Thorne takes some of the government reports to task for being incomplete assessments, and themselves not peer-reviewed.  The report concludes with a section assessing vibration, which is present, but well below levels considered problematic.  Addendums include a detailed assessment of noise complaints at several wind farms, including the Te Rere Hau wind farm in Palmerston North, New Zealand, where noise issues have occurred at far greater ranges than are observed elsewhere (surprisingly severe impacts are reported at distances of 2100-3100 meters, or almost two miles).

Most of the new wind turbine designs you see floating around the tech blogosphere are oriented toward small backyard turbines, in the tens or hundreds of kW range.  So it was kind of a thrill to see this new design for a 10MW offshore turbine, partly inspired by a spinning sycamore seed:

Aerogenerator X concept

After an 18-month feasibility study funded by a consortium of energy companies and the UK government, new funding and agreements are moving the project forward, with the goal of building a full-scale test version of the design by 2013 or 2014.  The current version is over 900 feet across, but half the height of vertical turbines (which would have the benefit of creating a markedly lower visual profile from shore, and even being “over the horizon” in many more near-shore locations).  The power-generating equipment sits at the bottom, rather than the top as in a tower, greatly reducing both the cost and complications of servicing. The horizontal design reduces pressure on the blades (which rotate just 3 times per minute), thus breaking through a stress barrier that will likely limit traditional turbine designs from moving much past the currently-envisioned 5MW size.  The drawback is that the lower profile will not access higher wind speeds at greater heights.

Here at AEI, we have great hopes for offshore wind, which moves the noise far from people’s homes, while tapping into a very consistent wind resource.  It’s not clear from the current news reports whether this design can be adapted to our ideal long-term scenario of floating turbine platforms (which allow deployment farther offshore in higher winds, and also greatly reduce the amount of loud construction noise, which is the primary impact off offshore wind on ocean acoustic ecology.) New conceptual technologies should always be treated as speculative, but this one does seem to be moving forward at a pretty good clip.  For more info:
Here’s the company press release, which has the most detail
And here are three blog reports on the announcement.

As noted here on AIEnews in May, a single new wind turbine in Falmouth, Massachusetts triggered noise problems for many nearby residents (12 formal complaints were filed, an unusually high number for any community, and residents of up to 45 of the 120 homes within a mile raised concerns in informal local meetings).  The town appears to have responded quickly: this news report from mid-June notes that the turbines had been shut off 39 times in the preceding month, when winds topped 22mph and noise would have been at its worst.  Both the town and a group of neighbors have hired lawyers and sound consultants to help them work through the situation; everyone spent a month discussing the nature of the noise issues as a study was designed to assess the conditions in which noise is the worst.  This recent article from the Falmouth Enterprise (sorry, no direct link found) summarizes the recent noise measurements made by both the town and residents’ sound consultants, and the first survey that recently took place.  Everyone seems to agree that the sound was much worse in its first three months of operation (March-May), when winds were higher, so it’s not altogether clear whether this survey, taken at a time when the air was quite hot and still, will suffice to answer the longer-term questions.

Falmouth is the second small New England town to run into unexpected noise problems after installing wind turbines in an effort to reduce electric bills and contribute to a sustainable energy future in their localities. Residents of Vinalhaven, Maine are also trying to find the balance between wind energy and local quality of life; AEInews has tracked their efforts since last December. It appears that Falmouth is being a bit more pro-active, as evidenced by the quick decision to shut down turbines in high winds.  By contrast, the sound study project proceeded a bit more slowly in Falmouth, which may also be a good thing; in Vinalhaven, there was some confusion and uncertainty as a noise survey commenced suddenly this winter, without much pre-consultation with neighbors of the turbines on the design of the study or the sorts of qualitative descriptors used on the surveys (which some neighbors found did not encompass the sounds they experienced).

This is new territory for every town that grapples with it; both Falmouth and Vinalhaven are at the forefront of constructively dealing with noise issues (especially in contrast most wind projects, where the turbines are owned by large and comparatively impersonal energy companies).  As more towns and energy co-ops consider erecting small wind projects, the lessons learned in Falmouth and Vinalhaven will serve to make the process of dealing with noise issues a bit easier elsewhere.

On July 13, I was honored to be one of three presenters in a webinar sponsored by the New England Wind Energy Education Project (NEWEEP), a DOE-funded project of Wind Powering America.  Complementing the technical and regulatory information presented by Mark Bastasch and Ken Kalinsky, my presentation focused on the “qualitatitive” data that we are receiving from people living near wind farms, which can be as useful as the quantitative data coming from engineers and scientists.  The main point of the presentation was that reports in wind farm communities, as well as our best research indications, suggest that a significant minority of nearby residents—25 to 45%—are quite seriously impacted by noise issues when sound is 40dB or more (roughly within a half mile); I also included a look at interesting research into rural place identity and noise sensitivity, both of which provide some clues as to why many people find wind turbine sounds very annoying, while other neighbors are not much bothered by them.

UPDATE, 8/4: All three presentations, along with the audio of the webinar and a transcript, can now be downloaded at the Wind Powering America website: http://www.windpoweringamerica.gov/calendar_past_events.asp Scroll down to “Understanding the Impacts of Wind Turbine Sound.” Mark’s presentation is largely about measuring sound; Ken’s focuses more on regulatory approaches.

A pdf version of the presentation can be downloaded here, or you can view or download the Powerpoint version via Slideshare:

I’ll be one of three presenters at what promises to be an informative 90-minute webinar taking place on Tuesday July 13.  It’s one of a series of wind energy programs being produced by the New England Wind Energy Education Project, a DOE-funded public information effort.  My piece will add a look at the experiential reports of wind farm neighbors, as well as the few studies we have that help clarify how common noise disturbances are around wind farms (hint: it’s much more than many people think, but also less than some believe); I also take a stab at understanding the variable responses of people hearing the same levels of sound/noise.  Joining me on the panel are Mark Bastasch, who will provide a primer on noise measurement and the sources of wind turbine sounds, and Ken Kalinsky, who will focus largely on the various approaches to regulating wind farm noise.  The three 20-minute presentations will be followed by a discussion and question and answer session that will last for roughly a half hour or so.

The webinar will take place on Tuesday July 13, from 2-3:30pm Eastern Daylight Time.  You must pre-register to receive login information.
For more information on this free webinar, see this PDF information sheet.  You can register from there by email; or, just use this email link and request registration information for Webinar #2.

Ontario’s environment ministry has released proposed siting guidelines for offshore wind turbines that set a minimum distance of 5km (3.1 miles) from shore.  The rules, which are now open for public comment, will be subject to public hearings in the fall. Ontario does not have ocean frontage; the rules are meant to govern wind farms planned for the Great Lakes.

The proposed standard would undermine some proposed wind farms, which are aiming to be 2-4km from shore.  It is likely that the proposal would greatly minimize the visual impact of turbines, and would may also reduce sound impacts to an acceptable level.  As noted in this brief essay, sound travels very easily over water, so that typical onshore setbacks could be insufficient for offshore sites.  Some reports from near the Wolfe Island wind farm (at the end of Lake Ontario, near the start of the St. Lawrence Seaway) suggest they are often quite audible from two miles, and occasionally somewhat audible at five to seven miles.  While there is often an assumption that wave sounds will easily drown out distant turbines, it’s likely that people living somewhat inland from the shoreline in otherwise very quiet rural areas would be the most affected by offshore turbine sounds.

Litchfield NY is considering a relatively flexible, while stringent, local ordinance to govern construction of wind farms.  As proposed by a committee of residents charged by the Town Council, the ordinance would avoid strict setback or decibel limits, and instead require easements to be obtained from all residents within 6500 feet of a turbine (just under a mile and a quarter).

The proposed ordinance now goes to the Council for consideration, where some changes are expected to be made.  Involving all neighbors who may be affected by new wind turbines could be a very effective approach, as both studies and experience shows that when people are involved in the decision to move forward with a wind farm (and compensated financially, or feel shared ownership), they are far less likely to have negative reactions and experiences.  I’m sure that the distance at which easements are required will be a sticking point for all concerned; as proposed, it encompasses a large grey area (from roughly 3500-6500 feet) in which acoustic effects are likely to be minimal, yet possible a small proportion of the time.  If the easements don’t effectively become vetoes, it’s quite likely that being involved in the decision could play a key role in this range.  Closer than a half mile or so, the proposed easements may well be sometimes used as a veto, as at least a few residents are apt to feel that the risk of noise issues is not outweighed by financial benefits in the project.  Still, the easement approach has many benefits over a strict decibel or setback limit, assuring that the developer is engaged with everyone who may be affected by the project.

An article in Der Spiegel reveals that the environmental impact study at a 12-turbine wind farm 30km off the coast of Germany has reported that during construction of the turbines, porpoises avoided an area in a 20-mile radius of the two-square mile construction site.  Harbor porpoises are well known to be more sensitive to sound than many ocean creatures, and may serve as a sort of “canary in the construction zone,” their stark behavioral response standing as an indicator of noise levels that likely interfere with other animals, as well.

Future construction could affect a far larger number of animals than the relatively modest construction that has taken place so far. (click to see larger Der Spiegel image)

This one passed under my radar in January, but has some potentially interesting implications for people working to minimize the negative effects of wind farms on wildlife and humans, in that the developer agreed to shut turbines down at night, at least temporarily.  In December, a Federal court halted construction of the Beech Ridge wind farm in West Virginia, because Indiana Bats, officially listed Endangered Species, live nearby, and the developers had not obtained the necessary Incidental Take Permits that govern activities that may impact such species.  In a settlement announced in January, Beech Ridge Energy, a subsidiary of Invenergy, agreed to forego construction of 24 turbines closest to the bat caves, while receiving approval to operate the 40 turbines that are already constructed, to complete construction of 27 more, and to move forward on planning for an additional 33 units (though the units not yet constructed may not begin operating until the ITP is received).

Most strikingly, the company agreed that all operational turbines will be shut down at night from April to November 15, when the bats are out and about.  During the hibernation season, from mid-November through March, the turbines can operate around the clock.  Future operating conditions, including the need for night-time curtailments, will be subject to the determination of the US Fish and Wildlife Service Incidental Take Permits. Noise is not the issue here, but rather bat mortality near wind turbines, likely caused by rapid changes in air pressure.

It is encouraging to see the viability of operational restrictions being experimented with, and accepted by  both industry and environmental groups as a way forward through a contentious issue.  Indiana Bats are not known to travel in the area of the wind farm, though the proximity of their caves suggests they may; monitoring done by the company was challenged in the lawsuit as insufficient.  Ongoing acoustic surveys will help clarify how common they are, and the USFWS may decide that night time restrictions are unnecessary.  As part of this settlement, the company agreed not to appeal the judge’s decision, and the environmental plaintiffs agreed not to appeal the eventual ITP decision by USFWS.

Happy talk all around after the agreement: Dave Burhman, spokesman for MCRE, said, “We believe our actions have sent a vitally needed message to the wind industry as a whole. Renewable energy projects do not get a pass on existing laws designed to protect endangered species and the natural environment. And although industrial wind turbines will now spin atop some of Greenbrier County’s highest ridges, they will forever be banned on those ridges in closest proximity to endangered Indiana bat caves.”  And Joe Condo, general counsel for the company, agreed that “We are very pleased to have reached an agreement that allows us to move forward with creating clean, renewable energy in Greenbrier County while at the same time meeting the goals of important wildlife conservation efforts.

Sources:
Beckley Register-Herald, 1/27/10
West Virginia Highlands Conservancy, 2/10/10

As noted in a previous post, a recent report by the Chief Medical Officer of Health (CMOH) in Ontario focused on the narrow question of whether there is a “direct causal link between wind turbine noise and adverse health effects” experienced by some wind farm neighbors.  Based on a review of published research, the answer was, “no.”  This week, two of the people who were on the review committee providing feedback on the report as it moved from draft to final form noted that the final version dropped a section that some reviewers had urged be included, which would have more directly addressed the actual experiences of communities near wind farms.

Dr. Hazel Lynn, the Grey Bruce medical officer of health, told the Owen Sound Sun-Times, “The whole section that a couple of us really wanted in there on community health and community disruption went. It’s not in there. I suspect politically she can’t criticize another ministry, so I was a little disappointed.”

“I think it’s a fair comment that there is other material that could have been in the report and wasn’t,” added Dr. Ray Copes, the director of environmental and occupational health at the Ontario Agency for Health Protection and Promotion and another member of the committee that reviewed drafts of the report. Copes said there are “really important and quite legitimate” questions about wind farms that he and Lynn thought should be discussed, but “I guess the CMOH’s report wasn’t the place for it.”

Both Lynn and Copes stressed that they agreed with the report as far as it went, and that direct noise levels and sound qualities of wind farms don’t appear likely to directly cause health problems.  Lynn noted that there is an “association” between wind farms and some health effects, but that these effects also occur elsewhere; still, she said, “Basically, I think they (wind farms) disrupt communities if they’re not properly planned and instituted and when you disrupt people’s communities they get sick.” There is evidence to back that position up, she added, but “that doesn’t come through very clearly” in King’s report. Likewise, Copes stressed that the idea of a unique quality in wind farm noise causing a new set of health problems seems “implausible,” yet he also stressed (as did AEI) that the report highlights the need for more direct measurements of sound levels around wind farms.  Such measurements will add much-needed ground truthing to the sound models currently used in siting decisions, and could provide more concrete data to use in assessing both noise complaints and health concerns.

An impressive array of 76 acoustic monitoring buoys is planned to be deployed in Scotland’s Moray Firth this summer, to listen in on local populations of dolphins, porpoises, whales, and seals.  Scientists from Aberdeen University will place the recording devices up to 70 miles offshore, expanding on work carried out last summer on a smaller scale.  Dr. Paul Thompson, one of the lead researchers, explains: “This will help us get a better understanding of the distribution of particular species. We will be looking at the impact primarily of oil and gas exploration, but also the development of wind farms. During construction phase of these developments, it can be quite noisy and affect marine mammals. It will allow us to get a better understanding of how they use different parts of the Moray Firth and to understand what parts are most important” to each species.  Read more at The Scotsman.

In recent months, several lawsuits and formal complaints have been filed, claiming unlawful nuisance and/or impacts on property values and quality of life near wind farms.  Most recently, sixteen residents sued the Michigan Wind I wind farm and its developers, laying out a series of complaints, including (as detailed in the Huron Daily Tribune):

• Private nuisance from, among other things, sustained and highly annoying audible noise and amplitude modulation in both audible and sub-audible frequencies
• Negligent design of a wind farm, including a noise assessment that estimated only audible noise levels within the dBA range, and did not consider low frequency noise or impulse noise
• Negligent misrepresentation, claiming the wind companies made false representations in board of commissioner and planning commissioner meetings and public hearings when company representatives said the wind farm’s operations would not result in a noise nuisance or cause adverse health effects to adjacent landowners. “(The defendants) were negligent in making these misrepresentations because, as the parties seeking approval to construct a wind turbine farm in Huron County, they had a duty to use reasonable care to provide Huron County and its citizens with both accurate and complete information,” the lawsuit states. The plaintiffs claim the wind companies provided inaccurate and/or incomplete information about the audible turbine noise levels, and no information about low frequency noise, infrasound and/or impulse noise emitted from the turbines.

In Pennsylvania, the Allegheny Ridge Wind Farm settled out of court this week as a lawsuit brought by Todd and Jill Stull was moving toward a jury trial in July.  The suit alleged that the company misrepresented the noise levels that would be generated by assuring residents the noise would e minimal.  The agreement is bound by confidentiality, so no details are available. See earlier coverage of the lawsuit here.

Meanwhile, in neighboring Wisconsin, Read the rest of this entry »

This recording, by one of the wind farm neighbors in Wisconsin who I met when visiting there last fall, is a good, simple taste of the sounds heard from 1500 or so feet away—this one has a predominant jet plane flavor, though often neighbors report a wide variety of sounds that change depending on wind conditions.  Most of these folks have several turbines around their homes; one person told me that he thought he could live with it if the ones closer than a half mile were not there, though another of his neighbors leaned more toward a mile as his comfort zone.  Listening to this selection of sounds, recorded with different cloud covers and wind directions, I could get a sense of why some people find hearing this incredibly disruptive and intrusive, while others say they are not much bothered; this disparity of reaction is one of the fundamental paradoxes of wind farm noise issues.  

Give a listen…..turn it up and down to get a feel for it at different sound levels or distances (or to simulate how it feels to people with different degrees of sensitivity/attention to the sound)…..imagine it lasting far longer than this three minute taste—which may well make it more torturous, or might allow it to sink into the background of your awareness…..if this sound, at a moderate level, or turned down very low to be just audible, was happening in your neighborhood, how would it be for you?

Over the past week or so, two reports from Ontario have spurred a fair amount of notice and comment among those following wind development issues.  First, the provincial health office responded to the public’s concerns about health problems reported by some wind farm neighbors, framing its answer carefully and narrowly:  ”According to the scientific evidence, there isn’t any direct causal link between wind turbine noise and adverse health effects,” said Dr. Arlene King, Ontario’s Chief Medical Officer, as reported by the Vancouver Sun.  Since the report’s focus was to asses peer-reviewed science, its authors did not incorporate any reference to the experiences or changes in sleep patterns or health of real-life neighbors of wind farms who have reported negative impacts since the turbines began turning. It is no real surprise that the sound levels near wind farms aren’t loud enough to directly cause physiological damage or effects, though it seems clear that annoyance and sleep disruption may well contribute to health effects in some people; the report acknowledges the likelihood of some annoyance, and notes too that while low-frequency sound is below generally perceptible levels, and generally no louder than naturally-occuring low-frequency sound sources, some people who hear these frequencies better than most may be bothered.  While the report itself is brief and lacks the detail of the recent industry-funded AWEA/CanWEA report, which reached similar conclusions in addressing the same narrowly-focused questions, King’s report frames the results with two crucial but under-reported observations:

• By way of introduction, the report explicitly states a simple fact that is rarely acknowledged: “Little information is available on actual measurements of sound levels generated from wind turbines and other environmental sources. Since there is no widely accepted protocol for the measurement of noise from wind turbines, current regulatory requirements are based on modelling.”  Indeed, sound models are used to determine what distance a turbine needs to be from nearby homes in order to meet local statutory noise limits (which stand at 40dB in Ontario).
• And in its final words, the report stresses the corollary to this observation: “The review also identified that sound measurements at residential areas around wind turbines and comparisons with sound levels around other rural and urban areas, to assess actual ambient noise levels prevalent in Ontario, is a key data gap that could be addressed. An assessment of noise levels around wind power developments and other residential environments, including monitoring for sound level compliance, is an important prerequisite to making an informed decision on whether epidemiological studies looking at health outcomes will be useful.”

Actual rural ambient noise levels are often very low, so that wind farm noise becomes bothersome at lower levels than industrial or transportation noises prevalent in urban and suburban areas; and, as noted in the body of the report, most of the case studies and other reports of health effects lack any clear information on how loud the turbine sounds are in the homes of those being affected.  So while this report is in large part another seemingly definitive, yet stubbornly partial, assessment of the health effects reported near wind farms, it also lays the groundwork for much-needed on the ground assessment of noise patterns around wind farms. (See this more recent post, regarding a section on community health and disruption that was omitted in the final draft of this report.  And see this critique of the CMOH report, written by several doctors from Canada, the UK, and the US who have been advocating for closer study of these issues)

On a similar note, Ontario Ministry of Environment officials confirmed this week that they do not have the capability to record or assess the noise near wind farms where noise complaints arise.  According to the Windsor Star, “Although hundreds of wind turbines have already been built in Ontario, Michael Parker, district manager for the environment ministry, said staff have not yet been given noise-monitoring equipment. The ministry is responsible for ensuring that wind turbine noise reaching a residence doesn’t exceed 40 decibels, he said.  If a complaint about turbine noise is made to the ministry, two environment officers are sent to the area to listen for the noise and contact the turbine owner, Parker said, noting that the ministry could still intercede with turbine owners even without hard data on the noise levels. In some cases, turbine speeds have been scaled back or the turbine shut down completely.”  In January, the Ministry of Environment issued two Requests for Proposals seeking advice and technical standards to use in assessing wind farm noise. The RFPs said that “The Ministry requires a consultant to assist in the development of a measurement procedure to assess noise compliance of existing wind farms with the applicable sound level limits,” noting that ”Unlike typical industrial noise sources, measurement of audible noise from wind turbines in general raises technical challenges.” At that time, the Ministry acknowledged that its “Noise Guidelines for Wind Farms…do not contain a measurement method for assessing the actual noise impact.”

The Morrow County Planning Board ruled this week that the Willow Creek Energy Center, an 80-turbine wind farm, is producing noise levels that violate Oregon’s noise limits, and gave Invenergy, the wind farm’s owner, six months to get the turbines into compliance.  The wind farm began operating in January 2009, and by March, several neighbors within a half mile had raised serious concerns about the noise (see this article for details), including regularly having difficulty sleeping. Noise monitoring then took place, and in January of this year, the Planning Board received the results, which showed that noise levels at four homes sometimes exceeded the limit of 37dB.

There was some contention at that meeting, as neighbors had hired independent noise monitoring consultants, whose records showed more consistent violations than those of the Invenergy-hired consultant; the differences were pegged to the fact that the Invenergy consultant did not record in high wind speeds, contending that the noise gets no louder above wind speeds of 9m/s.  It is unclear from initial news reports whether the wind farm will be required to comply with the noise limits based on the Invenergy sound monitoring protocol, which found excess noise just 10% of the time at one house, and less frequent slight violations at three others, or whether they’ll use the more comprehensive techniques used by the local citizens, which found violations more consistently at two homes (one just over the limit, the other often over 40dB), with one home experiencing excess noise on 22 out of 37 nights.

Carla McLane, Planning Director for Morrow County, noted that while the commission did rule the wind farm was violating state regulations, it found the turbines only crossed the noise threshold at certain times of day and under certain conditions. ”Some would want to view it in black and white and if it’s a violation then you have to shut them down,” McLane said.  ”Others would want to view it in terms of shade of gray and say it’s not an ongoing and continuous violation. It’s an intermittent violation.”

”I’m not sure how someone can say this is an unusual, infrequent event,” said Kerrie Standlee, one of the neighbors’ noise consultants. “To me, 59 percent (of nights with excess noise) is not occasional or unusual.” Standlee’s noise study also went beyond Invenergy’s in that he gave the residents a sheet of paper to log their experiences with time and date. He then overlaid those comments on the data and showed that when the residents reported high noise, the wind was blowing from a particular direction or at a particular speed.  This last bit of information may offer Invenergy some direction about when they might shut down turbines if they want to avoid the worst of the noise issues, during the six months they have to get into compliance.

The Planning Board struggled with the conflicting approaches, according the the East Oregonian (article archived here). ”I have a very hard time coming to a concrete conclusion on which study I feel is accurate,” Commissioner Pamela Schmidt said. “I’m not a licensed engineer in acoustics myself and there’s been so much information I can’t make a decision.”  Invenergy claimed that the background ambient noise varies, so that in higher wind periods, it should be allowed to exceed 36dB; yet, in its permit, it used the 26dB ambient standard, which is the state’s default if measurements are not made ahead of time. Complicating matters more is the fact that, as the East Oregonian noted, “the rule does not direct agencies on how to administer the rule or decide conflicts such as the one between Invenergy and its neighbors. The agency that originally enforced the rule, the Oregon Department of Environmental Quality, has since defunded and destaffed its noise program.”

It’s worth noting that the noise issues seem to be quite pronounced even at sound levels of 40dB.  Oregon’s 36dB limit is among the most conservative in the country; it’s based on being 10dB above average night time ambient noise levels, which have been measured at 26dB.  It appears that noise issues may well be present even when the measured sound levels are at or very near 36dB; this is in synch with reports from elsewhere, which suggest that people accustomed to quiet rural night time soundscapes are quite easily disturbed when turbine noise becomes one of the loudest local sounds, even when absolute noise levels are not extreme. In general, acousticians consider a sound to become readily audible when it is 5dB above ambient, with disturbance considered likely when it reaches 10dB above ambient.