Utility-grade turbines make audible sound (we can hear it) and low-frequency sound (we can’t hear it, but our bodies react). Low-frequency sound is measured with specialized instruments and the results interpreted by experienced audiologists or engineers. Low-frequency sound has been studied for decades by researchers in buildings, airplanes, rock concerts and by the Army.
Turbines make many audible sounds: swooshing from air passing over the blades, and thumps or whines from the motor in combination with the blades. The type and loudness of sound is influenced by temperature, closeness of other turbines, ground winds, upper winds and turbine size.
Bigger turbines make more audible and much more low-frequency noise. Because they are tall, their sounds travel out and then down, so we can stand underneath a turbine and hear only a soft whooshing, while a half-mile away others will hear a jet plane taking off all day. In hilly terrain, audible sounds can travel over a mile and low-frequency sounds up to six miles. Low-frequency sound passes through walls and into the body, where it causes vibrations that affect cell structure. Some can feel this, others cannot, but all living creatures are affected: www.wind-watch.org/documents/category/health/?titles=on
The primary health effect is disrupted sleep, which can cause serious disease: www.cadillacnews.com/news_story/?story_id=1816722&year=2014&issue=20140308. The longer we are exposed, the more likely we are to have health problems: inner ear damage, migraines, high blood pressure, immune diseases, dizziness, lethargy. Changes in the brain, particularly in children, can cause learning problems, and children seem more affected by low-frequency sound. The best explanation is here: www.wind-watch.org/documents/low-frequency-noise-and-health-a-wind-turbine-case-2007-2013/ .
Scientists cannot yet predict exactly where turbine sound will travel or who will be affected: http://oto2.wustl.edu/cochlea/wind.html and www.wind-watch.org/documents/problems-related-to-the-use-of-the-existing-noise-measurement-standards-when-predicting-noise-from-wind-turbines-and-wind-farms/. Scientific researchers on noise and health report serious health problems under .87 mile: www.noiseandhealth.org/article.asp?issn=1463-1741;year=2012;volume=14;issue=60;spage=237;epage=243;aulast=Nissenbaum.
Victoria L. Brehm
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