Monday, September 24, 2007

Wind turbines and noise

From abstracts of papers presented at the Wind Turbine Noise 2007 conference, Sept. 20-21, Lyon, France:

"In wind turbines the drive train, especially the gear box, is a significant source of noise. Significant contributions come from the gear mesh and from resonances of the structure like the main frame or the torque arm. The structure-borne noise from these sources is transferred either to the rotor or to the tower and radiated to the environment. The contributions to the noise spectrum from these sources are single tones in the frequency range from about 100 Hz to about 600 Hz."

--paper describing passive and active vibration absorbers manufactured by the German company ESM

"The larger proportion of the general population who live far from them think wind turbines are great -- while the smaller proportion representing people with homes near where wind turbines were subsequently erected have concerns, particularly about noise. On a popular vote basis, as seen by elected officials, the choice is clear, but on a justice basis, who looks out for the impacted few? ...

"The results for one wind farm, the Kingsbridge wind farm near Goderich Ontario, which has the closest distance between the wind turbines and the Environment Canada weather office monitoring station, show that about 31% of the hours of the year show an unmasked noise output above the Ontario Standard, and for nearly 10% of the hours of the year, the noise is significantly above the provincial standard (over 3 dBA), in many cases about 10 dBA above the background level produced by the wind at the receptor. In the 6 months from October 2006 to March 2007, on 64% of the days, there were hours of unmasked noise. This demonstrated the problem to be chronic and significant in nature. For another Ontario wind farm, the results in the summer period between May 1st and August 31st, 2006 showed 59% of the days demonstrated the problem, with it occurring 48% of the nights, and 33% of the nights showing the condition sustained for 3 or more hours. ...

"The presentation will go through the results in detail. They will show that the current Ontario interpretation by the Ministry of the Environment is not adequate to protect the public from excessive annoyance."

--William K. G. Palmer, Canada

"Previous studies have shown that wind turbine noise could be annoying at sound pressure levels lower than those known to be annoying for other community noise sources, such as road traffic. This could be due to the special characteristics of wind turbine noise (amplitude modulation) that make the sound easily perceptible. It could furthermore be due to atmospheric situations influencing large modern wind turbines more than older ones, leading to higher sound exposure than accounted for in the planning process."

--Eja Pedersen, Sweden, and Jelte Bouma, Roel Bakker, and Frits van den Berg, the Netherlands

wind power, wind energy, wind farms, wind turbines, human rights, animal rights