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Wind-turbine noise impacts

Most people are surprised how quiet modern wind turbines are when they visit a wind farm. Mechanical noise is usually minimal – even right up close. And the aerodynamic blade noise is often less than the noise of wind in any trees or bushes near by. However in some locations some problems have still been reported.

An international panel of experts convened by the American and Canadian Wind Energy Associations, recently released a report based on a review of a large body of scientific literature on sound and health effects with regard to sound produced by wind turbines. After extensive review, analysis and discussion, the panel concluded that sounds or vibrations emitted from wind turbines have no adverse effect on human health – an issue that was recently given new prominence by a US report, which claimed that physiological damage could be caused by low-frequency sound from wind turbines (see my earlier blog).

The new review states:

• There is no evidence that the audible or sub-audible sounds emitted by wind turbines have any direct adverse physiological effects.
• The ground-borne vibrations from wind turbines are too weak to be detected by, or to affect, humans.
• The sounds emitted by wind turbines are not unique. There is no reason to believe, based on the levels and frequencies of the sounds and the panel’s experience with sound exposures in occupational settings, that the sounds from wind turbines could plausibly have direct adverse health consequences.

Even so, there are still reports that aerodynamic “swishing” sounds from wind farms are an issue at some sites at night – disturbing some people’s sleep. The Telegraph quoted a nurse, Jane Davis, who says that she was forced to move from her home in Lincolnshire after eight wind turbines were built in 2006. “All I know is the amount of health problems people have suffered,” which she said included sleep deprivation, tinnitus, depression and psychological stress “seem to be excessive”. She added: “These things have devastated my life.”

The AWEA/CWEA report does say that, although “work with low frequencies has shown that an audible low frequency sound does not normally become objectionable until it is 10 to 15 dB above hearing threshold”, an exception is “when a listener has developed hostility to the noise source, so that annoyance commences at a lower level”. They note that “a major cause of concern about wind turbine sound is its fluctuating nature; some may find this sound annoying, a reaction that depends primarily on personal characteristics as opposed to the intensity of the sound level” and report that a “study of more than 2000 people suggested that personality traits play a role in the perception of annoyance to environmental issues, such as sound”.

However, they add, a bit abruptly perhaps, that though “some people may be annoyed at the presence of sound from wind turbines; annoyance is not a pathological entity”. It’s certainly true that once a noise gets annoying, however low the level (e.g. a tap dripping), it can become intolerable.

The report concludes that, though “there is no evidence that sound at the levels from wind turbines as heard in residences will cause direct physiological effects…a small number of sensitive people, however, may be stressed by the sound and suffer sleep disturbances”.

That rendition may not please sufferers! Of course, you could say that road traffic and aircraft landing and taking off can lead to much more noise annoyance for a lot more people, as can city living. But should we be adding more stress? Rural areas are, after all, usually quieter, which is one of their attractions. Or, assuming it cannot be resolved by careful wind-turbine location or modified operational patterns, is that just a cost that has to be borne by a small minority, who might in any case find a conventional power plant near them significantly less attractive?

The government’s view certainly seems unchanged. NewEnergyFocus reported that in January, energy minister David Kidney dismissed claims that the permitted night-time noise limit for onshore wind turbines is too high. He said that the 43 dB night-time limit in the ETSU-R-97 guidance was derived from the sleep disturbance criteria in Planning Policy Guidance 24, with an addition to allow for an open window. He said that ETSU-R-97 gave indicative noise levels thought to offer “a reasonable degree of protection to wind farm neighbours” and that there was no evidence that they needed to be reviewed. He added that residents’ comfort had to be balanced with the needs of wind-farm developers and so the guidelines should not place unreasonable restrictions on wind-farm development or add unduly costs and administrative burdens on wind-farm developers or local authorities. He concluded: “We have no robust new evidence to suggest that the current guidance is not achieving its aim.”

AWEA/CanWEA report

Posted by Dave Elliott on February 6, 2010 8:00 PM | Permalink