Excellent report by Lisa Linowes: The deceit of turbine noise models

The Deceit of Turbine Noise Models (collateral damage from government energy forcing)
by Lisa Linowes
October 19, 2011
reprinted from Master Resource

“When will the environmentalist community writ large wake up to the unintended micro consequences of their increasingly futile macro policy of forced energy transformation?”

Herkimer County, New York, is the latest location to register wind turbine noise complaints. The source? Iberdrola’s Hardscrabble wind facility (37 turbines) that went online earlier this year.

Studies are underway to determine if the project is operating outside legal sound limits, but the larger question is “Why?” Why, with over 1,300 MW of wind installed in New York today and an extensive body of evidence showing turbine noise is causing deleterious impacts on people living near the towers, was Herkimer County fooled into thinking it would be spared?

The answer is simple: Herkimer County residents were lied to.

Yes, we could use softer words to explain the situation. But given what sound experts already know about turbine noise, the time for niceties has passed.

Predicted Turbine Noise at Hardscrabble

Prior to erecting a wind facility, project owners usually engage acoustic engineers to prepare models that predict sound level increases a community can expect from an operating project at certain reference points. These engineers rely on the CADNA/A [1]software tool for their models. CADNA/A is based on ISO 9613-2, the international standard developed for sound prediction.

The CADNA/A tool generates predicted sound levels at various distances from the turbines. Developers present the sound levels as contour lines overlaid around the turbine sites. Each contour shows a sound level in decibels with the lines closest to the turbines having higher decibel levels.

The sound predictions developed for Hardscrabble showed that during periods of low wind conditions, non-participating residents closest to the turbines could expect to experience noise increases of less than 6 dBA over the presumed existing level of 35 dBA. During high wind conditions, modeled data showed property owners would experience slightly higher levels but most increases would still be under 6 dBA [2].

Prior to construction, Iberdrola insisted the facility would meet the New York state noise guidelines for most situations and would be in full compliance with local regulations that limited noise to 50 dBA.

CADNA/A and the ISO 9613-2 Standard

Acousticians hired by the wind industry insist the ISO standard is an appropriate method for modeling wind turbine sound provided the correct input parameters are used. But what they do not admit is that the ISO 9613-2 standard, on which CADNA/A is based, was never validated for wind turbine noise. In fact, the standard is mainly applicable to situations concerning road or rail traffic, industrial noise sources, construction activities, and many ground-based noise sources. It does not apply to sound from aircraft in flight, to blast waves from mining, military, or other similar operations. And it was not designed to predict turbine noise.

The ISO Standard limits use of its methods to noise sources that are close to the ground (approximately 30 meter difference between the source and receiver height) and within 1 kilometer of the receiving location. A wind turbine with a hub height of 80+ meters exceeds the ISO height limit by 50 meters. Meteorological conditions are also limited to wind speeds of approximately 1 meter/second and 5 meters/second when measured at a height of 3 meters to 11 meters above the ground.

Only when all of these constraints are met by the situation being modeled can the predicted noise levels be assumed to be accurate within a +/- 3 dB range.

The constraints placed on the ISO standard having to do with wind speed, direction and weather conditions indicate just how limited the models are for anything other than simple weather conditions — NOT the types of conditions that wind turbines need to operate.

The way sound spreads outdoors can be affected by temperature differences in different layers of the wind that cause sound waves to bend up or down at the boundaries just like water bends light. If a noise source is above a boundary then sound that would have gone down to the ground surface might bend up and dissipate. If the noise source is below a boundary layer then sound that might have dissipated upwards is bent down and added to the sounds that would normally be directed downwards. The current science of meteorology does not have precise ways to know what is happening right near any particular turbine.

Heinrich A. Metzen of DataKustik GmbH [3], maker of CADNA/A confirmed this fact in an e-mail where he stated:

“long range propagation including atmospheric refraction is not part of the standards used for (normal, “standard”) noise calculations. It is known that atmospheric refraction may cause sound to be refracted downwards again and contributing strongly to the level at long distances. The atmosphere in the standards existing is just homogeneous above height.”

Since there are no accepted algorithms to predict these refractions, sound propagation models cannot evaluate conditions that have vertical or horizontal turbulence even though we know they can add significant sound at the receiving location when present. As a result, predicted sound levels are understated.

Countries in the European Union are developing their own models for predicting turbine noise propagation because of their concerns with limitations of the ISO standard. Unlike the ISO 9613-2 standard, these newer models have been validated for turbine noise by peer-reviewed independent studies.

Iberdrola Knows Better

The first post-construction sound study in Herkimer revealed noise levels reaching 60 to 65 decibels, nearly 20 decibels above what was predicted for homes in the area. Iberdrola’s Paul Copleman told the press that the excessive noise levels were largely due to the wind rustling leaves and cannot be “attributable to the wind farm.”

Seriously? Any guesses on the number of complaints filed over noisy leaves before the turbines were sited?

Use of a model that understates real-world operational sound levels is very likely the root cause of the problem at the Hardscrabble facility.

Acoustic experts who work for the wind industry, including Iberdrola, are well aware of the limitations of the ISO modeling. They are well aware that the standard is intended for ground-based sound sources and has never been validated for predicting wind turbine noise. They also know that literature on turbine noise dating back nearly a decade has shown that these models underestimate wind turbine noise levels. But here in the U.S., wind industry acousticians still use the CADNA/A tool without qualification.


Herkimer County residents are now suffering the consequences of an environmentally intrusive, government-enabled industrial project. Moreover, they were lied to.

When will the environmentalist community writ large wake up to the unintended micro consequences of their increasingly futile macro policy of forced energy transformation?


[1] The CADNA/A software tool is written and sold by DataKustik GmbH of Munich, Germany.

[2] The 6 dBA figure comes from New York’s published guidance which states “In non-industrial settings the [Sound Pressure Level] should probably not exceed ambient noise by more than 6 dB(A) at the receptor. An increase of 6 dB(A) may cause complaints.”

[3] Email from H. Metzen, DataKustik GmbH, manufacturer of CADNA/A software, Nov. 16, 2006.


Lisa Linowes is Executive Director and spokesperson for the Industrial Wind Action (IWA) Group, a national advocacy focused on the impact/benefits analysis and policy issues associated with industrial wind energy development. As publisher and editor of the IWA website, http://www.windaction.org, she tracks news and research pertaining to industrial wind, and facilitates information sharing on the issue.

1Ed Reid { 10.19.11 at 7:25 am }
Were we dealing with anything other than the “fair haired boy” of the environmental community, the solution would be glaringly obvious. Either monitor the noise emissions from the project and fine the owners / operators for each violation; or, require that the project be shut down until it could be brought into compliance.

However, in this instance, the folks in Herkimer will probably just have to learn to live with the “sounds of environmental progress”. At least they’ll be able to tell when the wind is blowing. (sarc off)

2Jon Boone { 10.19.11 at 9:51 am }
Nice analysis. The notion that wind noise is little more than the wind rustling leaves is by now an old AWEA dodge. And the use of half-backed scientific techniques by pundits on the take is an even older dodge. In the wind business, the powerful odor of mendacity pervades virtually all claims justifying the technology, made possible because there is absolutely no penalty for lying in the wind energy marketplace.

Even when this mendacious behavior is exposed via accurate testing, the defendants will no doubt use the old dodge of “plausible deniability” to justify their actions. That is, they’ll say they hired the best experts who used the latest technology–and that they didn’t know their methods were flawed. The courts and the regulators, which themselves were complicit in the fraud, will give the wind LLC’s yet another pass. While the affected residents will be consoled by all with words like “some must sacrifice if we are to have the clean, green energy from the wind.” Another lie, of course, but that’s yet another story….

For years, I’ve studied the claims of wind industry developers, their trade organization, the American Wind Energy Association, and the National Renewable Energy Lab, an agency of the US Department of Energy, with staff whose jobs are dependent upon the success of renewable technologies and who routinely engage in revolving door employment with AWEA. I’ve concluded that industrial wind energy exemplifies American business at its worst, promising to save the environment while wreaking havoc on it. Spawned, then supported, by government welfare measures at considerable public expense, it produces no meaningful product or service yet provides enormous profit to a few wealthy investors, primarily multinational energy companies in search of increased bottom lines. It’s an environmental plunderer, with its hirelings and parasites using a few truths, many half-truths, and the politics of wishful thinking to frame a house of lies. It’s all a bill of goods. Not a single claim made for industrial wind energy is true.

3Daily News & Views – October 20, 2011 | JunkScience.com { 10.20.11 at 1:01 am }
[…] The Deceit of Turbine Noise Models (collateral damage from government energy forcing) “When will the environmentalist community writ large wake up to the unintended micro consequences of their increasingly futile macro policy of forced energy transformation?” […]

4J Burton. { 10.20.11 at 6:35 am }
I am assuming that the CADNA/A software predicts the sound pressure levels of audible sound. Their predictions might well be the best available.
However, Annoyance seems related to the intensity levels of the inaudible sound also generated by turbines.
As far as I am aware this inaudible energy impact is never even considered in setting planning conditions.

Few developers would constrain schemes financially to minimise an adverse impact which is immediately detectable by an unknown proportion of observers. That is, unless there is a relevant planning condition.

‘Low Frequency Noise- LFN ‘ is an acute problem for the minority of observers who are pre-conditioned. Of sufficient magnitude it can cause new sensitisation. What is needed is published research into the effects of LFN and the magnitudes generated by Turbines.

5Jon Boone { 10.20.11 at 8:01 am }
J Burton:
Your observations are right on target. Low frequency noise does indeed seem to be the main source of serious health problems emanating from wind turbines. The phenomenon and its affects–and not just on humans–merits much more study, given its highly nuanced aspect. But more research dollars for this work seems yet another casualty of the lost opportunity costs of throwing so much of the public’s lucre down the rathole of wind.


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