A recently-released report by Dr. Christopher Hanning, a UK MD whose specialty is sleep disorders, takes a comprehensive look at factors affecting sleep disturbance caused by nearby wind farms, and is highly recommended reading for anyone working to develop regulations at the local or state level.  Hanning’s primary point is that external noise need not WAKE a sleeper to cause problems, and the repeated “arousals” can break the most restful periods of sleep.  He notes that “The sleep, because it is broken, is unrefreshing, resulting in sleepiness, fatigue, headaches and poor memory and concentration.”  These are precisely the symptoms often reported by people living near wind farms. He stresses that arousals are also associated with “physiological changes, an increase in heart rate and blood pressure, which are thought to be responsible for the increase in cardiovascular risk. Arousals occur naturally during sleep and increase with age (Boselli 1998) which may make the elderly more vulnerable to wind turbine noise. Arousals may be caused by sound events as low as 32 dBA and awakenings with events of 42dBA (Muzet and Miedema 2005), well within the measured noise levels of current wind farms” and the levels permitted by most jurisdictions.

The report also summarizes other studies suggesting that night-time noise levels are often higher than sound models predict, as well as one that suggests that wind farms cause high levels of annoyance at lower sound levels than other common noise sources.  He concludes that “While it may be possible to produce a reasonable acoustically based theoretical approach to calculating set back distances (Kamperman and James 2008b), it makes more sense to rely on recommendations from observations of the effects on real people at established wind farms.”

Download the full report here.

Thanks to Lynda Barry at National Wind Watch for the heads up.