“Health effects due to low-frequency components in noise are estimated to be more severe than for community noises in general” - World Health Organization [1] 

Wind turbines generate a broad spectrum of noise including low frequency noise and infrasound which may be audible or inaudible. [2],  [3], [4],  [5]

It is widely affirmed that exposure to audible low frequency noise can cause adverse health effects in humans. [6], [7], [8], [9]

Low frequency noise can cause “…immense suffering to those who are unfortunate to be sensitive to low frequency noise and who plead for recognition of their circumstances.” [10]

“Wind turbines are generally located in areas devoid of trees and other large vegetation. Instead, ground cover usually consists of grass, sagebrush, plants, and low shrubs, which are minor impediments to noise propagation except at very high frequencies. At frequencies below about 1000 Hz, the ground attenuation is essentially zero.” [11]

The farther away from the wind turbine the greater is the low frequency content due to a relatively larger atmospheric absorption of high frequencies. Considering the A-weighted sound level outdoors in relevant distances to neighbours, the lower frequencies constitute a substantial part of the noise. [12]

There is no doubt that as wind turbines get larger and more densely sited the lower frequency part of the noise spectrum is of importance to the neighbours' perception of noise from large wind turbines. Noise from wind turbines is under certain atmospheric conditions more annoying and - especially the low frequency part - spread much farther than generally accepted.  Wind turbines may cause low frequency noise induced annoyance both inside and outside a building. [13]

Peer reviewed articles and other references acknowledge annoyance to be an adverse health effect.[14],[15], [16], [17]

“Regulatory authorities must accept that annoyance by low frequency noise presents a real problem which is not addressed by the commonly used assessment methods.” [18]

Literature reviews and peer reviewed scientific articles confirm the symptoms associated with low frequency noise exposure include annoyance, stress, sleep disturbance, headaches, difficulty concentrating, irritability, fatigue, dizziness or vertigo, tinnitus, heart ailments anxiety, stitch and beating palpitation. [19], [20], [21]

International research and media reports document people exposed over time, to too-close wind turbines, are experiencing adverse health effects.  “These symptoms include sleep disturbance, headaches, difficulty concentrating, irritability and fatigue, but also include a number of otologic symptoms including dizziness or vertigo, tinnitus and the sensation of aural pain or pressure.” [22]

The American Wind Energy Association and Canadian Wind Energy Association sponsored literature review entitled “Wind Turbine Sound and Health Effects” acknowledges wind turbine noise may cause annoyance, stress and sleep disturbance and as a result people may experience adverse physiological and psychological symptoms. The literature review specifically acknowledges that wind turbines may cause low frequency noise induced annoyance. [23]

More specifically Geoff Leventhall, a coauthor of the wind energy association sponsored “Wind Turbine Sound and Health Effects” states

“The symptoms of… Wind Turbine Syndrome...sleep disturbance, headache, tinnitus, ear pressure, dizziness, vertigo, nausea, visual blurring, tachycardia, irritability, problems with concentration and memory, and panic attack episodes associated with sensations of internal pulsation or quivering when awake or asleep…I am happy to accept these symptoms, as they have been known to me for many years as the symptoms of extreme psychological stress from environmental noise, particularly low frequency noise.” [24]

World Health Organization advises that “Health effects due to low-frequency components in noise are estimated to be more severe than for community noises in general…The evidence on low-frequency noise is sufficiently strong to warrant immediate concern.” and consequently “Noise with low-frequency components require lower guideline values.” [25]

The effects of low frequency noise induced annoyance and stress may be serious and it is acknowledged that “The claim that their "lives have been ruined" by the noise is not an exaggeration…” [26]

It is acknowledged that “…LFN (low frequency noise) does not need to be considered “loud” for it to cause such forms of annoyance and irritation.” [27]

“The effects of infrasound or low frequency noise are of particular concern because of its pervasiveness due to numerous sources, efficient propagation, and reduced efficiency of many structures (dwellings, walls, and hearing protection) in attenuating low frequency noise compared with other noise.” [28]

“Unlike higher frequency noise issues, LFN is very difficult to suppress. Closing doors and windows in an attempt to diminish the effects sometimes makes it worse because of the propagation characteristics and the low-pass filtering effect of structures. Individuals often become irrational and anxious as attempts to control LFN fail, serving only to increase the individual’s awareness of the noise, accelerating the above symptoms”  [29]

“Those exposed may adopt protective strategies, such as sleeping in their garage if the noise is less disturbing there. Or they may sleep elsewhere, returning to their own homes only during the day.” [30]

Some individuals have resorted to sleeping in a tent [31], been billeted by the wind energy proponent, [32], [33] or have abandoned their homes [34], [35] to escape the wind turbine noise that has invaded their home.

Wind turbine produce infrasound which may be inaudible or audible.

A spectral analysis of sounds emitted at a Michigan site revealed that unweighted peak levels at frequencies under 5 Hz exceeded 90 dB SPL (Wade Bray, pers. comm., 2009). [36]

“There is no doubt that some humans exposed to infrasound experience abnormal ear, CNS, and resonance induced symptoms that are real and stressful.” [37]

There is no scientific consensus that infrasonic noise below the threshold of hearing will have no effect on health. There is scientific uncertainty regarding the understanding of human response to infrasound. 

“There is no consensus whether sensitivity below 20 Hz is by a similar or different mechanism than sensitivity and hearing above 20 Hz…” [38]

In a 2009 Environmental Review Report [39] for an Ontario, Canada wind turbine project the consultant acknowledged that regarding wind turbine low frequency noise (LFN) and adverse health effects:

“It is acknowledged that LFN may be one area of scientific uncertainty in the wind industry as a whole.”

and regarding wind turbine infrasound:

“…it is recognized that this may be an area of scientific uncertainty.”

The National Research Council states “Low-frequency vibration and its effects on humans are not well understood. Sensitivity to such vibration resulting from wind-turbine noise is highly variable among humans…. studies on human sensitivity to very low frequencies are recommended.” [40]

The conclusions of a 2010 peer reviewed scientific article states

“1) Hearing perception, mediated by the inner hair cells of the cochlea, is remarkably insensitive to infrasound.

2) Other sensory cells or structures in the inner ear, such as the outer hair cells, are more sensitive to infrasound than the inner hair cells and can be stimulated by low frequency sounds at levels below those that are heard. The concept that an infrasonic sound that cannot be heard can have no influence on inner ear physiology is incorrect.

3) Under some clinical conditions, such as Meniere’s disease, superior canal dehiscence, or even asymptomatic cases of endolymphatic hydrops, individuals may be hypersensitive to infrasound.

4) A-weighting wind turbine sounds underestimates the likely influence of the sound on the ear. A greater effort should be made to document the infrasound component of wind turbine sounds under different conditions.

5) Based on our understanding of how low frequency sound is processed in the ear, and on reports indicating that wind turbine noise causes greater annoyance than other sounds of similar level and affects the quality of life in sensitive individuals, there is an urgent need for more research directly addressing the physiologic consequences of long-term, low level infrasound exposures on humans.” [41]

It is incorrect to assume that inaudible low frequency noise cannot cause adverse health effects as “…non-aural physiological and psychological effects may be caused by levels of low frequency noise below the individual hearing threshold.” [42]

“Low-frequency noise may also produce vibrations and rattles as secondary effects.” [43]

“Although infrasound levels from large turbines at frequencies below 20 Hz are too low to be audible, they may cause structural elements of buildings to vibrate.” [44]

“Jung and colleagues (2008), in a Korean study, concluded that low-frequency noise in the frequency range above 30 Hz can lead to psychological complaints and that infrasound in the frequency range of 5–8 Hz can cause complaints due to rattling doors and windows in homes.” [45]

Field studies and “…research has shown that the acoustic energy from wind turbines is capable of resonating houses, effectively turning them into three-dimensional loud speakers in which the affected residents are now expected to live. The phenomenon of natural resonance combines to produce a cocktail of annoying sounds which not only disturb the peace and tranquility once-enjoyed by the residents, but also stimulate a number of disturbing physiological effects which manifest in the physical symptoms...” [46]

A NASA technical paper on wind turbine noise states

“People who are exposed to wind turbine noise inside buildings experience a much different acoustic environment than do those outside….They may actually be more disturbed by the noise inside their homes than they would be outside….One of the common ways that a person might sense the noise-induced excitation of a house is through structural vibrations. This mode of observation is particularly significant at low frequencies, below the threshold of normal hearing.” [47]

Living conditions are acknowledged to be a key determinate of health. [48]

A World Health Organization epidemiology study confirms disturbed living conditions caused by noise increases the risk of ill health. [49]

Peer reviewed scientific research confirms “Pollution and degradation of the indoor environment cause illness, increased mortality, loss of productivity, and have major economic and social implications.…The health effects of indoor noise include an increase in the rates of diseases and disturbances… these illnesses, and the related reduction in human productivity, can result in substantial economic losses.” [50]

Modern upwind industrial wind turbines produce a characteristic audible modulation of aerodynamic noise. [51] This is commonly referred to as amplitude modulation and is acknowledged to contribute to higher levels of wind turbine induced annoyance and/or sleep disturbance in the exposed population. [52], [53], [54]

Wind turbine low frequency noise and infrasound is also modulated.

“Low frequency sound and infrasound are normal characteristics of a wind farm as they are the normal characteristics of wind, as such. The difference is that “normal” wind is laminar or smooth in effect whereas wind farm sound is non-laminar and presents a pulsing nature.” [55]

“A limitation of much work on assessment of low frequency noise has been that long term averaged measurements were used and, consequently, information on fluctuations was lost. Many complaints of low frequency noise refer to its throbbing or pulsing nature.” [56]

Research related to low frequency noise “…confirms the importance of fluctuations as a contributor to annoyance and the limitation of those assessment methods, which do not include fluctuations in the assessment.” [57] 

Adverse health effects associated with low frequency noise and infrasound can be avoided with authoritative regulations that ensure protection is engineered into the design of wind turbine projects.

Low Frequency Noise is an issue that must be resolved quickly and accurately to improve the sound environment and quality of life for the residents.  For this reason, it remains the duty of authorities to implement regulations that will account for low frequency noise.[58]

It is widely affirmed that A-weighting underestimates the sound pressure level of noise with low-frequency components. [59], [60], [61] , [62], [63] “A-weighted level is very inadequate…” [64] when assessing low frequency noise and infrasound.

C-weighting and Z-weighting are more appropriate to assess noise with low frequency components.

Globally the adoption of low frequency noise and infrasound regulations is hampered by wind energy industry resistance. For example in Canada the Ontario Ministry of the Environment determined that wind turbine developers be required “…to monitor and address any perceptible infrasound (vibration) or low frequency noise. [65] However CanWEA lobbies against having to address the impacts of wind turbine low frequency noise and infrasound “…CanWEA submits that the proposed requirement for infrasound or low frequency noise monitoring as a condition of the REA be removed.” [66]

Conclusions

Based on the best available science the following conclusions can be drawn.

·    Wind turbine noise is likely to be audible to receptors in the form of continuous low-level or intermittent swooshing, as well as low frequencies at approximately 50 Hertz.

·    Exposure to audible low frequency noise can cause adverse health effects in humans.

·    Humans must be protected from the adverse health effects of low frequency noise exposure.

·    Wind turbine low frequency noise may induce annoyance, stress and sleep disturbance which may have other health consequences.

·    International research and media reports document people exposed to wind turbines reporting adverse health effects. Reported symptoms include annoyance, stress, sleep disturbance, headaches, difficulty concentrating, irritability, fatigue, dizziness or vertigo, tinnitus and the sensation of aural pain or pressure.

·         Wind turbines emit infrasound which may be audible or inaudible. There is scientific uncertainty regarding infrasound; however, it is plausible wind turbine infrasound could adversely affect human health.

·    It is acknowledged infrasound can induce annoyance, stress and sleep disturbance by disturbing people inside their homes through structural vibrations.

·    Based on current understanding of how low frequency sound is processed in the ear, and on reports indicating that wind turbine noise causes greater annoyance than other sounds of similar level and affects the quality of life in sensitive individuals, there is an urgent need for more research directly addressing the physiologic consequences of long-term, low level infrasound exposures on humans.

·    Adverse health effects associated with low frequency noise and infrasound can be avoided with authoritative regulations that ensure protection is engineered into the design of wind turbine projects.

·    Members of the wind energy industry oppose addressing wind turbine low frequency noise and infrasound. For example the Canadian Wind Energy Association has lobbied against the introduction of protective guidance designed to address wind turbine low frequency noise and infrasound.