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There's one particularly big glitch in the positions promoted by Industrial Wind Turbine proponents when it comes to the audible sound levels put out by these turbines. This "glitch" is well illustrated by the Ontario Ministry of the Environment backgrounder for Proposed Requirements and Setbacks for Wind Turbines ...
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The backgrounder for the Ontaio Ministry of the Environment's backgrounder for Proposed Requirements and Setbacks for Wind Turbines states that their proposed regulations will "ensure noise levels do not exceed 40 decibels at the receptor. Forty decibels is approximately the noise level experienced in a quiet office or library."
The Proposed Content for the Renewable Energy Approval Regulation under the Environmental Protection Act states "Proposed setbacks in the noise matrix are consistent with the Ministry of the Environment’s Noise Guidelines for Wind Farms (October 2008) and the noise level limit of 40 dBA at the Point of Reception regardless of wind speed."
A "quiet office or library" is a tranquil environment condusive to both contemplation and concentration .. to work and reading .. without distractions or loud noises. We can honestly expect that a "quite office or library" would possess sound levels consistently no higher than 40 dBA.
However, in my opinion, the industry's and government's use of these comparisons, examples and figures is rife with misrepresentation and resulting deception. In typical highway noise studies, the Ontario Ministry of the Environment chooses to gather "One Hour Equivalent Sound Level", by averaging all the readings taken continuously over one hour. Unfortunately, this same methology has been adopted by both the Industrial Wind Turbine Industry and the regulating government agencies.
The audible sound produced by the industrial wind turbines is cyclical in nature, resulting from the three-bladed rotors rotating and producing their characteristic "whoosh, whoosh, whoosh". The "highway noise study" methodology fails to capture the fact that these regular, repeated cyclical instances of "whoosh" can substantially surpass the 40 dBA noise level limit during their individual durations. This same methodology also fails to recognize the contrasts in sound levels which occur with constant repetition .. in themselves extremely dynamic, distressful and distracting.
An extremely interesting explanation of Fast Response Sound Level Meters, Fast Meter Responses, Single Event Levels, and Impulse Sound Levels (dBAl) is to be found at the Royal Canadian Mounted Police's ...
www.rcmp-grc.gc.ca/cfp-pcaf/information/club/snd_guide/SRAS/SoundMeasurement.htm.
The repetitive and cyclical "whoosh" of an industrial wind turbine is truely "industrial" in nature .. definitely more akin to a mechanical production process or a repeated pistol discharge than the hum of distant traffic or the subtle sounds of a "quiet office or library". To replicate an industrial wind turbine's "whooshes" in a library, one would have to either repeatedly "rip-up" all the metal venetian blinds or repeatedly dump books from the shelves .. with the same repetitive frequency of the turbine's "whooshes". But, oh dear, you would no longer be in a "quiet library"!
This ambiguity is a big glitch in the positions promoted by Industrial Wind Turbine proponents when it comes to the audible sound levels put out by these turbines.
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Incorrect Methodology For Measuring Audible Industrial Impact Noise An industrial wind turbines' typical "whoosh, whoosh, whoosh" audible sounds are cyclical industrial-impact sounds. Government agencies have incorrectly chosen to use the 'average-over-time' method of measurement to determine their decibel levels. This method was designed for continuous sound mixtures of low-differential components .. such as those consistently produced by busy highways and ventilation systems.  |
The following informative and helpful reference "Comparative Examples of Noise Sources, Decibels & Their Effects" is found on the website of Industrial Noise Control Inc. of North Aurora, Illinois ...
audible.htm (June 29, 2009)