photo by Keith Park via flickr.
A new study done on the visual and aural impact of wind farms has been released and contains some findings that are sure to generate debate among proponents and detractors of wind energy.
The EU-financed WINDFARMperception study is a collaborative effort by researchers at the University of Gronigen, the University Medical Centre Gronigen and the University of Gothenburg. Begun in 2006, the purpose of the study was to examine the perceptions of Dutch residents living within 2.5km of a wind turbine. The main focus of the research was to determine levels of annoyance due to aural and visual exposure to the turbines. In selecting which areas to study, only wind turbines of 500kW or more and with a spacing of 500m or less were included. Excluded were sites where the turbines had be installed or replaced within the last year.
The full WINDFARMperception report is available from the Univ. of Gronigen website, but the main points are summarized below:
Is Noise from Wind Farms Louder Than Expected?
As might be expected respondents increasingly noticed the sound from the turbines as decibel levels increased: 25% at 30dB or less; 80% at 35dB or more. There was no difference in noise perception based on whether the project economically benefitted the respondent.Perceived annoyance increased with decibel level: 2% at 30dB or less; 25% at 40-45dB. Interestingly, respondents receiving some sort of economic benefit from the project reported nearly no annoyance at any decibel level.
According to the authors' press release, "Three out of four participants declare that swishing or lashing is the correct description of the sound from turbines. Perhaps the character of the sound is the cause of the relatively high degree of annoyance."
Out of Sight Out of Mind
If respondents could see the turbine from their dwelling they were "far more likely" to perceive the turbine as annoying. Between 4-13% of respondents were "rather or very annoyed" by vibrations, the movements of rotor blades or their shadows.
Wind Farm Noise Masked by Other Sources
The report concludes that though other nearby noise sources (such as busy roadways or in industrial areas) did mask the perception of noise from the turbines, this masking did not have an effect on perceived annoyance. "Even much louder road traffic does not appear to reduce the annoyance due to wind turbine sound."