The Canadian Wind Energy Association (CanWEA) is not aware of any specific studies that have examined modifying gear ratios, and what effect this would have on sound.
CanWEA notes that the balance of credible, peer-reviewed research and key published literature reviews in the area of wind turbine sound and health clearly indicates that:
The wind industry acknowledges that wind energy developments, like any major development, may result in some community members experiencing annoyance to a varying degree, and that the overall response of a community towards a wind energy project is based on numerous variables, not solely attributable to the audible sound produced by a wind turbine.
As you are likely aware, there are two primary sources of sound from a wind turbine – mechanical and aerodynamic. Mechanical sound is produced from moving parts, gears, and other equipment in the wind turbine nacelle. While a component of the overall sound, mechanical sound has been reduced through improved insulation and overall design.
Aerodynamic sound constitutes the largest component of the audible sound a person hears from a wind turbine. The wind energy industry acknowledges that a small portion of individuals consider aerodynamic sound — which occurs over the low to mid frequency range — a source of concern. However, a number of studies have found this is not entirely due to sound itself. Visual or aesthetic concerns, poor community engagement, level of economic benefits, etc., have been shown to also affect how an individual may be affected by the presence of a wind turbine. With respect to the sound itself, research suggests that there are several sources of detection – tonality (low frequency sound) and more recently, amplitude modulated sound (the typical “swooshing”,) are cited as being the most obvious to individuals.
Despite the above, wind energy is universally recognized as one of the safest and most environmentally friendly sources of electricity available to us today. The balance of scientific evidence and human experience to date clearly shows that wind energy is not harmful to humans. Please consult several international reviews on this matter that have engaged dozens of scientific, medical, and acoustics experts.
You can find more links and resources related to wind energy and health on the Health Page. Please do not hesitate to contact us for more information at firstname.lastname@example.org.
The WindFacts Team