Resource Documents: Infrasound (3 items)
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Author: Deever, Donald Allen
June 1, 2019 – Desert Report: Sierra Club California/Nevada Desert Committee
Sci-fi fans remember the tagline from the Alien movie poster, which ominously declared, “In space, no one can hear you scream.” Likewise, research on the infrasound frequencies produced by industrial wind turbine blades is increasingly providing proof that what you can’t hear, can hurt you. Accordingly, it is worth noting that there is a huge difference between the auditory terms “sound” and “noise.” According to the Canadian Centre for Occupation Health and Safety, “Sound is what we hear. Noise is unwanted sound.” When speaking of the sounds generated by industrial wind turbines, the operative term is “noise,” and an important difference between sound and noise – including when infrasound noise is not heard by the ears – is that it can be felt by the brain and internal organs. Such an insight makes it all the worse to learn that infrasound noise can travel over much longer distances than previously admitted by the wind energy industry. Moreover, the intensity of potentially harmful levels of infrasound vibrations do not dissipate as quickly as formerly believed.
Along those lines, an important German study calculated the distances over which wind turbines can have unanticipated effects. The 2016 study warned how wind turbine-produced infrasound interferes with Comprehensive Nuclear Test-Ban Treaty monitoring equipment that is operated by Germany in the Bavarian Forest and Antarctica. The purpose of those stations are to verify compliance with the International Monitoring System that exists to detect nuclear explosions occurring in the atmosphere. The conclusion of that study suggested that a distance of 20 kilometers between a single wind turbine and the monitoring stations should be considered a rule of thumb and that a separation of 50 kilometers should be maintained between multi-element wind energy facilities and monitoring stations. The introduction to that article tells of a variety of studies that already took place to identify the hazards that wind turbine infrasound were already wreaking on similar monitoring stations on Ascension Island, as well as a station in southern California where the monitoring equipment is located 35 kilometers from a so-called “wind farm.” Moreover, the historical portion of that study mentioned, “Wind turbine noise effects on seismometer stations have also been investigated and reported for example at AS104 station in Eskdalemuir, UK. Stammler and Ceranna investigate the increasing influence of wind turbines on seismic records, depending on the wind speed and on the number of newly build wind turbines in the vicinity of seismic sensors.” This suggests that wind turbine infrasound could interfere with the monitoring and prediction of earthquakes and associated tsunami warnings.
The great distances that infrasound waves travel from their source was also documented in a study by the Los Alamos and Sandia Laboratories, published in 2014. In New Mexico, infrasound from sixty wind turbines could be detected 90 kilometers from the source under favorable conditions at night. The present trend of the wind energy industry is to push for more offshore than onshore facilities, yet studies in acoustics show that sound waves travel further over water than land, and that cooler water temperatures create inversions that cause sound waves to bend downward and become amplified which is a thought that leads to a study in Finland.
A 2016 Finnish pilot study belatedly made international news in 2018, when the Finnish Association for Environmental Health studied 200 persons affected by wind turbine infrasound. The report showed the severity of adverse health symptoms did not decrease for the first 15 kilometers from the source. It also determined that the effects were not correlated with the expectations of the persons being studied. This represented a major finding, since few countries require more than a 2 kilometer setback of wind turbines from homes. The results of the Finnish study should not have been a surprise among occupational medical health professionals. In 1999, a report was published by the International Journal of Occupational Medicine and Environmental Health, which stated, “Owing to its long wavelength, infrasonic noise is less attenuated by walls and other structures, it is able to propagate over long distances and may affect the human organism even though the latter is far from its source.”
In light of the proliferation of wind energy, one might ask, “How long have the negative effects of wind turbine-generated infrasound been known?” The first solid evidence for estimating the levels of annoyance from infrasound on humans was found thirty-two years ago. In 1987, Neil Kelley pioneered the field of wind turbine noise annoyance when he presented a study at the WindPower ’87 Conference and Exhibition in San Francisco. His lecture was titled A Proposed Metric for Assessing the Potential of Community Annoyance from Wind Turbine Low-frequency Noise Emissions. That research was carried out at the Solar Energy Research Institute in Golden, Colorado, and sponsored by the U.S. Department of Energy. Kelly’s lab-based report directly linked infrasound to annoyance among human subjects, thereby indirectly linking stress-related disorders from annoyance to wind turbine infrasound.
Since infrasound lies in the inaudible frequency range of less than 20 Hertz, “What you can’t hear, can’t hurt you” was a mantle of protection the wind industry hid under for decades. Few governments embrace the concept of wind energy as enthusiastically as Germany, yet a highly-publicized 2017 report from their Max Planck Institute found that infrasound, even though it is inaudible, can produce measurable effects in recorded brain function. According to their report, “this study is the first to demonstrate that infrasound near the hearing threshold may induce changes of neural activity across several brain regions, some of which are known to be involved in auditory processing, while others are regarded as key players in emotional and autonomic control.”
This 2017 study from the Max Planck Institute, “Altered Cortical and Subcortical Connectivity Due to Infrasound Administered Near the Hearing Threshold – Evidence from fMRI”, also broached the topic of increased cortisol secretions that occur as a result. According to the authors of that report, “since the brain’s response to prolonged near-threshold IS [infrasound] involves the activation of brains areas which are known to play a crucial role in emotional and autonomic control, a potential link between IS-induced changes of brain activity and the emergence of various physiological as well as psychological health effects can be established.”
Citing earlier research, the authors stated, “It has been reported in several studies that sustained exposure to noise can lead to an increase of catecholamine and cortisol levels. In addition, changes of bodily functions, such as blood pressure, respiration rate, EEG patterns and heart rate have also been documented in the context of exposure to below- and near-threshold IS (infrasound).” The references to those citations are contained in that study. Equally enlightening is a study that was published fifteen years earlier (2002) in Sweden, “Low Frequency Noise Enhances Cortisol Among Noise Sensitive Subjects During Work Performance.”
Pre-dating the research from the Max Planck Institute, back in 1985, infrasound was similarly found to increase secretions of the hormone cortisol (causing a flight or fight response), which, at sufficiently high levels, can stress the body and mind to trigger annoyance, apathy, confusion, fatigue, an inability to concentrate, and painful pressure in the ears, all of which represents merely short term symptoms. Too much cortisol in the long term eventually weakens immunosuppressive action, weight gain, brain damage, hyperglycemia (elevated blood sugar levels that lead to diabetes), and a shut down of digestive and endocrine functions. In the end, prolonged cortisol production can lead to hypertension. Fast-forward approximately 25 years to 2011, when Canada’s Environmental Review Tribunal made history by officially declaring that the health debate is no longer whether wind turbine noise is harmful to human health but has evolved into one of the degree of harm, Erickson v. Director, Ministry of the Environment. 2011. Environmental Review Tribunal Nos. 10-121 and 10-122. A simple experiment to witness the end of the debate over wind turbine noise can be seen by going to Google Scholar and observing the results from searching the terms “wind turbine” AND “health effect” together.
On January 26, 2019, congratulations were issued by Cape Cod Wave Magazine to the people of Falmouth, Massachusetts, following their long fight to win a court decision to have a wind energy facility removed from their town. The courts sided with neighbors when it was demonstrated beyond a reasonable doubt that the harmful effects of infrasound emanating from the wind turbines did not justify their existence, and therefore the company was ordered to cease operations and dismantle the towers. Such a legal pronouncement indicates that an understanding concerning the adverse effects of industrial wind turbines has advanced beyond the realm of political opinion and moved into the arena of evidence.
Next month: Part 2 of this series will explore research on potentially harmful effects on animals, pets and wildlife, and will look at the facts or fantasy of President Donald J. Trump’s recently criticized comment that wind turbine infrasound can cause cancer.
Dr. Donald Allen Deever is a former park ranger, science teacher, flight instructor, freelance journalist, and PhD with majors in nursing education, software development, and writing pedagogy. He recently helped defeat the Crescent Peak Wind project in Southern Nevada, one of the most misplaced wind energy developments in history. He and his wife live in Searchlight on their own ten-acre nature preserve.
Download original document: “Silent Menace (Part 1 of 2): Wind Turbine Infrasound – What You Can’t Hear Can Hurt You”
Author: Salt, Alec
Presentation by Alec N. Salt, PhD, Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri, USA, at the Symposium on Adverse Health Effects of Industrial Wind Turbines, Picton, Ontario, October 29-31, 2010.
[Download a PDF of the presentation slides from the link at end of this article.]
Wind turbines generate infrasound.
Wind turbine infrasound is at levels that cannot be heard.
Widely cited interpretations:
- “If you cannot hear a sound … it does not affect you.” – Leventhall G. What is infrasound? Progress in Biophysics and Molecular Biology 2007; 93:130–137
- “Infrasound is negligible” – DELTA. Low Frequency Noise from Large Wind Turbines 2008
- “Infrasound … is below the audible threshold and of no consequence” – Leventhall G. Canadian Acoustics 2006; 34:29-36.
This logic seems to be applied only to hearing. Consider other senses:
- Taste: If you can’t taste it, it can’t affect you? Can you taste salmonella?
- Smell: If you can’t smell it, it can’t affect you? Try breathing pure CO or CO₂
- Sight: If you can’t see it, it can’t affect you? Photokeratitis, “snow blindness”, “welder’s flash”, cataracts, sunburn: Ultraviolet (UV) light is invisible; even though you can’t see it, UV does affect you. UV can harm you.
“If you can’t hear it, it can’t affect you” is only true:
If no other part of the ear is more sensitive than hearing, and
If no other part of the body is more sensitive than hearing …
and I will show this is not true.
Infrasound at moderate levels is detected by the ear.
Infrasound at levels generated by turbines affect the ear.
Vibrations cause a bending of the ear’s sensory hairs. The inner hair cells are connected to auditory (type I) nerve fibers that send signals to the brain. You “hear” with your inner hair cells.
Inner (IHC) and outer (OHC) hair cells respond differently as sound frequency is changed. IHC respond to velocity. OHC respond to displacement. OHC respond at ~40 dB below IHC sensitivity at 2 Hz.
Outer hair cells will be stimulated by wind turbine noise.
Outer hair cells do not just detect sound:
For low-amplitude high frequencies, OHC elongate when hairs are bent outwards, which makes stimulus greater for IHC (amplifies signal).
Amplifier becomes less effective (less necessary) for higher level sounds, ineffective about 40 dB above threshold
(Reichenbach T, Hudspeth AJ. Proc Natl Acad Sci U S A 2010)
High-Frequency stimulus: OHC elongate; Vibration amplitude at the IHC is amplified.
At very low frequencies, we know that bending the hairs laterally causes OHC to contract.
Infrasound stimulus: OHC contract; Vibration amplitude at the IHC is reduced.
OHC are detecting low-level infrasound and actively canceling it for the IHC.
Physiologic pathway exists for infrasound at levels that are not heard to affect the brain. The idea that infrasound effects can be dismissed because they are inaudible is incorrect.
Infrasound => OHC => (via type II nerve fibers) subconscious brain: ear fullness, ear pressure, discomfort, alerting/sleep disturbance
A-weighting corrects a sound measurement to represent what is heard, based on the human audibility (40 phon) curve. At 1 Hz, −148 dB correction, equivalent to dividing by 25 million.
Effect of A-weighting wind turbine noise: Massive (140 dB) de-emphasis of infrasound component. A-weighting may represent what you hear – but hearing does not give a reliable indication of whether the infrasound is affecting your ears.
“A-weighting” principle applied to UV light is equivalent to adjusting sunlight spectrum for what is visible and then saying: “There is nothing here that can harm you. You don’t need sunscreen. You don’t need sunglasses. Go spend all day laying out in the sun.” This approach isn’t rational when applied to light, so why do we accept similar logic applied to sound?
Measuring visible light (e.g., photographs) tells you NOTHING about UV content. Similarly, A-weighted measurements tell you NOTHING about infrasound content.
A-weighted spectra totally misrepresent the effects of wind turbine noise (that includes infrasound components) on the ear.
A-weighted level readings (e.g., 42 dBA) are totally meaningless for assessing whether turbine noise is affecting the ear.
Documenting Wind Turbine Sound
• Most video cameras do not record the infrasound component of wind turbine noise.
• Speaker systems in TVs and computers cannot play back the infrasound component.
• Even if they did – you can’t hear it!
• Video recordings of wind turbines give no indication of the infrasound level being produced.
• Infrasound can only be measured with specialized instrumentation capable of detecting sounds down to ~1 Hz.
G-weighting weights infrasound components (excluding higher frequencies) according to human sensitivity curve.
G-weighted turbine measurements: For most of these conditions, the ear will be stimulated by the turbine noise. Jakobsen J. Infrasound emission from wind turbines. Journal of Low Frequency Noise Vibration and Active Control 2005; 24:145-155.
Other ways that infrasound could affect the ear:
Stimulation of vestibular hair cells (saccule, utricle).
- Vestibular hair cells are “tuned” to infrasonic frequencies.
- No-one has ever measured sensitivity to acoustic infrasound.
- Symptoms: unsteadiness, queasiness
Disturbance of inner ear fluids (e.g. endolymph volume).
- Low-frequency sound at non-damaging levels induces endolymphatic hydrops (a swelling of one of the fluid spaces).
- Infrasound does affect endolymph volume – it is the basis of a treatment for hydrops (Ménière’s disease).
- No one has ever measured what level of infrasound causes hydrops.
- Symptoms: ear fullness, unsteadiness, tinnitus
Infrasound – affected structures and long-term exposure effects, ranked by sensitivity:
- Outer hair cells – “Overworked, tired, irritated” OHC, type II fiber stimulation
- Inner ear fluid homeostasis – Volume disturbance, endolymphatic hydrops
- Saccular hair cells – Stimulation
- Other, non-ear, receptors – Stimulation
- Inner hair cells/hearing – None
Sensitivity and sensations remain to be quantified: ear pressure or fullness, discomfort, arousal from sleep; ear fullness, tinnitus, unsteadiness; unsteadiness; stress, anxiety.
“Wind Turbine Syndrome” – You cannot hear what causes the symptoms!
We need more research to define the sensitivity of these processes.
Sounds you cannot hear …
Can affect you.
Can disturb you.
Can harm you.
Can cause disease: auditory and balance disorders, effects of sleep deprivation are serious (hypertension, diabetes, mortality).
Conclusion and Recommendations
For years, people have been told that infrasound you cannot hear cannot affect you. This is completely wrong.
Because the inner ear does respond to infrasound at levels that are not heard, people living near wind turbines are being put at risk by infrasound effects on the body that no one presently understands.
Until a scientific understanding of this issue is established we should not be dismissing these effects, but need to be erring on the side of caution.
For industrial turbines a cautious approach could require :
- Setbacks of at least 2 kilometers (1-1?4 miles).
- In-home monitoring of both A-weighted (audible) and G-weighted (infrasound) noise levels 24 hours/day for all dwellings within 2 miles.
- Health monitoring studies for those living within 2 miles (with consent).
We need to stop ignoring the infrasound component of wind turbine noise and find out why it bothers people!
Wind turbine noise is not comparable to the rustling of leaves.
Download original document: “Infrasound: Your ears ‘hear’ it but they don’t tell your brain”
Author: Ceranna, Lars; Hartmann, Gernot; and Henger, Manfred
- Number of wind turbines and their size are constantly growing
- Wind turbines and wind farms generate strong infrasonic noise which is characterized by their blade-passing harmonics (monochromatic signals)
- Generated noise of wind turbines can theoretically be estimated
- geometrical spreading ≈ R−1
- SPL ≈ rpm4
- Recordings from field measurements near a single wind turbine show that the theoretical model is also valid for frequencies below a few Hz
- Minimum distance between an infrasound array and a wind farm can be estimated to avoid reduction of the array’s detection capability (e.g. 600MW wind turbine: d >15 km, 11-element wind farm: d >30 km)
Presented at the Infrasound Workshop, November 28 – December 02, 2005, Tahiti
Lars Ceranna, Gernot Hartmann, and Manfred Henger
Federal Institute for Geosciences and Natural Resources (BGR), Section B3.11, Stilleweg 2, 30655 Hannover, Germany
Download original document: “The inaudible noise of wind turbines”