Schomer, et al, Wind Turbine Noise Conference, Denver, August 2013
A proposed theory to explain some adverse physiological effects of the infrasonic emissions at some wind farm sites
5th International Conference on Wind Turbine Noise
Denver August 2013
Paul D. Schomer, John Erdreich, James Boyle, Pranav Pamidighantam
Dr Paul Schomer and his colleagues have contributed a very important advance in our understanding as to why a small subsection of total number of residents adversely impacted by wind turbine noise (and perhaps other sources of infrasound as well) become immediately unwell when exposed, and are so severely affected by the emissions that they resort to leaving their homes or workplaces.
This paper does not deal with the most commonly reported adverse health effect of the residents, which is sleep deprivation, itself an acknowledged adverse health effect. But it does establish a mechanism for direct causation which is supported by the clinical evidence.
The theory proposed on the basis of the acoustic survey findings at Shirley Wind Project Wisconsin, supports and extends research by Dr Nina Pierpont, who was the first medical practitioner to establish the relationship between people who were particularly adversely affected by wind turbine noise and motion sickness, and the connection with the vestibular system. This work also complements and builds on the work of neurophysiologist Alec Salt in this area.
Selected quotations from the paper follow
“For at least four decades there have been reports in scientific literature of people being made ill by low-frequency sound and infrasound. In the last several years there have been an increasing number of such reports with respect to wind turbines, which corresponds, obviously, to their becoming more prevalent. A study in Shirley, WI has lead to interesting findings that include:
(1) for major effects, it appears that the source must be at a very low frequency, about 0.8 Hz and below with maximum effects at about 0.2 Hz;
(2) the largest, newest wind turbines are moving down in frequency into this range;
(3) the symptoms of motion sickness and wind turbine acoustic emissions “sickness” are very similar;
(4) and it appears that the same organs in the inner ear, the otoliths may be central to both conditions.
Given that the same organs may produce the same symptoms, one explanation is that the wind turbine acoustic emissions may, in fact, induce motion sickness in those prone to this affliction. Finally, It is shown that the probability that sensitivity to motion sickness and sensitivity to wind turbine acoustic emissions are unrelated is less than 2 in 1,000,000. “
“The measurements support the hypothesis developed above that the primary frequencies are very low, in the range of several tenths of a Hz up to several Hz. The coherence analysis shows that only the very low frequencies appear throughout the house and are clearly related to the blade passage frequency of the turbine. As Figures 4 shows, the house is acting like a cavity and indeed at 5 Hz and below, where the wavelength is 60 m or greater, the house is small compared to the wavelength.”
“Most residents do not hear the wind-turbine sound; noise annoyance is not an issue. The issue is physiological responses that result from the very low-frequency infrasound and which appears to be triggering motion sickness in those who are susceptible to it“
“It has been shown that the probability that sensitivity to motion sickness and sensitivity to wind turbine acoustic emissions are unrelated is less than 2 in 1,000,000. This statement is sufficient to make clear a relation between wind turbines and motion sickness symptoms in what appears to be a small fraction of those exposed. This finding does not prove our hypothesis that the otoliths are responding to the wind turbine infrasonic emissions. Rather, we can say that the pathway for inducing this condition appears to be the same as airborne transmission through the middle ear and thence to the vestibular sensory cells, but confirmatory research of the pathway is recommended. “
“Finally, it is shown that the force generated on the otoliths by the pressure from the infrasonic emissions of the wind turbines is perhaps 1.5 to 3 times larger than the force that would be generated by an acceleration that was in accordance with the US Navy’s Nauseogenic Criteria (Figure 7 herein). That is, a 0.5 to 0.7 Hz “tone” at 74 dB produces about the same to 1.5 times the force as does a 2 m/s2 acceleration. “
“The effect shown here for wind-turbine emission is certainly not unique to wind turbines. Rather, it appears that these effects would occur with any low infrasonic source. This finding may explain some of the reports that have been present in the literature for over 40 years.”
Additional research and data collection recommendations
“Currently the wind turbine industry presents only A-weighted octave band data down to 31 Hz, or frequently 63 Hz, as a minimum. They have stated that the wind turbines do not produce low frequency sound energies. The measurements at Shirley have clearly shown that low frequency infrasound is clearly present and relevant. A-weighting is inadequate and inappropriate for description of this infrasound. In point of fact, the A-weighting, and also the C and Z-weightings for a Type 1 sound level meter have a lower tolerance limit of -4.5 dB in the 16 Hz one-third-octave band, a tolerance of minus infinity in the 12.5 Hz and 10 Hz one-third- octave bands, and are totally undefined below the 10 Hz one-third-octave band. Thus, the International Electro-technical Commission (IEC) Wind Turbine measurement standard needs to include both infrasonic measurements and a standard for the instruments by which they are measured.“