Apprehension surrounding the noise caused by turbines is among the most oft-voiced concerns in preparing for a wind development. However, in reality, a well-placed and properly setback wind farm produces very little objectionable noise. Below, you'll find links to a variety of studies that have analyzed the noise surrounding turbines, as well as relevant quotations from each.
W. David Colby, M.D. : Chatham-Kent Medical Officer of Health (Acting); Associate Professor, Schulich School of Medicine & Dentistry, University of Western Ontario and Geoff Leventhall, Ph.D.: Consultant in Noise Vibration and Acoustics, UK are the experts and presenters on this issue.
Colby and Leventhall have both determined that Pierpont’s study methodology is flawed:
- Small Study Sample: Pierpont based her results only on telephone interviews with 10 families, amounting to 38 people.
- Self-reported, Self-selected, Self-published: Pierpont selected all the subjects herself through an open survey and self-published her book.
- No Diagnostic Testing Conducted; Unverified Symptoms: She failed to physically meet with any of her case study subjects. No physical examinations or diagnostic tests were performed to verify the symptoms she wrote about.
- Extreme Study Selection Bias: Pierpont admits on page 124 of her book “…I chose the cluster of the most severely affected and articulate subjects I could find…I endeavored to protect against exaggeration by including in the study only families who had moved out of their homes or done something else expensive in response to their symptoms, proving their symptom severity in ways other than words.” These statements somehow presume that extreme actions verify the existence of Wind Turbine Syndrome, not actual diagnostic tests.
- Main Sources Used Are Misrepresented: Pierpont has clearly misunderstood much of the acoustic material which she refers to. The only support which Pierpont gives is a paper by Todd and colleagues (Todd, N., Rosengren, S. M., and Colebatch, J. G. (2008): Tuning and sensitivity of the human vestibular system to low frequency vibration. Neuroscience Letters 444, 36 - 41.), which she claims as “direct experimental evidence of such vestibular sensitivity in normal humans.” Her use of this paper is very puzzling, indeed alarming because the paper does not deal with air conducted sound.
Todd, himself, has even made a public statement that his study does not relate to “Wind Turbine Syndrome”:“Our research is being cited to support the case that “wind turbine syndrome” is related to a disturbance of vestibular apparatus produced by low-frequency components of the acoustic radiations from wind turbines. Our work does not provide the direct evidence suggested.”
- Pierpont Has Not Made Any New Discoveries: She is describing stress effects of low level noise that only occur with a small number of people. Her effects are well-known and documented as environmental noise problems.
Following review, analysis, and discussion of current knowledge, the panel reached
consensus on the following conclusions:
There is no evidence that the audible or sub-audible sounds emitted by wind turbines have any direct adverse physiological effects.
The ground-borne vibrations from wind turbines are too weak to be detected by, or to affect, humans.
The sounds emitted by wind turbines are not unique. There is no reason to believe, based on the levels and frequencies of the sounds and the panel’s experience with sound exposures in occupational settings, that the sounds from wind turbines could plausibly have direct adverse health consequences.
Some have indicated their belief that setbacks of more than 1 mile may be necessary. While the primary purpose of this study was to evaluate the potential for adverse health effects rather than develop public policy, the panel does not find that setbacks of 1 mile are warranted."
In the USA, a high profile objector (Nina Pierpont of Malone NY) placed an advertisement in a local paper, consisting entirely of selected quotations from a previously published technical paper by van den Berg (Van den Berg 2004). However the comment “[i.e. infrasonic]”, as shown in Fig 3, was added in the first line of the first quotation in a manner which might mislead naive readers into believing that it was part of the original.
The van den Berg paper was based on A-weighted measurements and had no connection with infrasound.
The comment, [ i.e. infrasonic], added into Fig 3 gives incorrect information. Claims of infrasound are irrelevant and possibly harmful, should they lead to unnecessary fears."
The infra-sound, when measured as dBG with the G-weighting scale, was found to be not audible, approximately between 15 – 20 dB below the threshold of perception, indicating that modern wind farms do not generate infrasound levels that are perceptible."
Ramakrishnan then specifically reputes van den Berg, the author of the report cited in Pierpont's advertisement:
There are no studies cited in van den Berg’s work that show a correlation between modulated sound and annoyance and hence van den Berg conjectures the annoyance would be worse since the expected amplitude variations make the perception of the sound strong. However, no evidence other than anecdotal responses was forthcoming."
When discussing infrasound from wind turbines, it is particularly important to distinguish between turbines with downwind rotors and turbines with upwind rotors. Some early wind turbines did produce significant levels of infrasound; these were all turbines with downwind rotors. The downwind design is rarely used in modern utility-scale wind power turbines.
There is no reliable evidence that infrasound below the perception threshold produces physiological or psychological effects."
This shows that in terms of the number of people affected, wind farm noise is a small?scale problem compared with other types of noise; for example the number of complaints about industrial noise exceeds those about windfarms by around three orders of magnitude.”
Although there is the possibility of effects on people exposed to noise in the low-frequency sound and infrasound range of frequencies, the effects would only ever occur when the sound is audible (above the hearing threshold). The evidence available is that the level of emissions of low frequency sound and infrasound from wind turbine generators is so low that it is inaudible. There is no reliable evidence to indicate any effects on people when infrasound is present at an inaudible level (below the hearing threshold).
There is no evidence to indicate that low-frequency sound or infrasound from current models of Wind Turbine Generators should cause concern.”
Infrasonic levels created by wind turbines are often similar to the ambient levels prevalent in the natural environment due to wind, typically 85 dBG or lower, and there is no evidence of adverse health effects caused by this infrasound. Infrasound near modern wind turbines is generally not perceptible to humans, either through auditory or non-auditory mechanisms. There is often an audible ‘swoosh’ created by wind turbines, which is essentially broadband noise whose amplitude is modulated at a low frequency, but this should not be mistakenly confused with infrasound. All in all, based on Canadian and international studies, infrasound generated by wind turbines should not be considered a concern to the health of nearby residences.”