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Acoustics scientists criticize  

Credit:  By Axel Pihl-Andersen (Journalist, Jyllands-Posten) | 1 July 2013 | ~~

Vestas has just launched a global campaign, which according to the wind turbine-giant itself is a counter-attack on the anti-wind movement, which is to be put in place by the pioneering Act on Facts-campaign.

“For too long, the wind industry has allowed itself to be run over by few, but influential anti-wind movements, arguing with half truths and wild myths. Vestas now responds with a fact based global campaign, which aims to turn the passive majority of people into active advocates of wind power.” These are among the words in Vestas’ press release, which states, that the campaign shall replace “hardlived myths and lies about wind energy with documented facts”. But Vestas has large problems with the documented facts themselves, says Denmark’s leading acoustics scientists at Aalborg University.

Noise from a refrigerator

One of the campaign’s major topics is noise, and Vestas claims, that the noise 400 meters away from a wind turbine is less than the noise from an average refrigerator. But that is pure nonsense, says acoustics professor Henrik Møller from Aalborg University.

“If you take a sound level meter and measure on your refrigerator, it will register a noiselevel of approx. 30 dB. The sound pressure level for a wind turbine at a distance of 400 meters will be approx. 40-43 dB, and that is a very big difference. If the noise level of a refrigerator were 40 dB, it would be impossible to sell”, says Henrik Møller.

He believes that Vestas, in spite of its facts-campaign, has messed seriously around with the acoustic terms. Producers of refrigerators do announce some noise levels of about 40 dB, but according to Henrik Møller, these refer to a technical measure called the sound power level, and this cannot be compared to the sound pressure level.

Two different types of decibel

“I think they have compared the sound power level from the refrigerator with the sound pressure level from wind turbines, and those are two very different measures. Decibel is not just decibel – it depends on what you are measuring”, says Henrik Møller.

Press officer and spokesman Jens Velling from Vestas admits that there is some “uncertainty” about this information. “We are aware of it, but I want to point out, that the campaign first launched is designed for Australia, where the required distance between a windturbine and a residence is 800 meters. At this distance, the numbers make sense”, says Jens Velling.

But you write 400 meters in your material?
“Yes, that is something we need to rephrase”.

It is not a good thing that you present wrong information in a campaign that is supposed to be based on facts, is it?
“No, you are right about that. It is essential, that the information we give is correct. We need to take a look at that phrasing.”

Professor Henrik Møller states, that the numbers don’t make sense at 800 meters distance either, where you, at a wind speed of 8 meters per second for a 3 MW Vestas wind turbine with a sound power level of approx. 107 dB, will measure a sound pressure level of approx. 37-38 dB. This is still somewhat away from the refrigerator’s 30-32 dB.

The National Association for Neighbours of Large Wind Turbines in Denmark also criticizes Vestas’ campaign for manipulating with numbers and information. “Vestas’ campaign contains much misleading information, but worst is the assertion that the noise of a wind turbine at a distance of 400 meters compares to that of a refrigerator”, they write in a press release.

Source:  By Axel Pihl-Andersen (Journalist, Jyllands-Posten) | 1 July 2013 |

This article is the work of the source indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.

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