Infrasound Emissions Research Articles

A low-order simulation model for wind turbine infrasound prediction

Wind energy is one of the fastest-growing renewable energy technologies. One of the environmental concerns associated with wind energy development is noise emission from wind energy facilities, especially the low-frequency noise and infrasound that allegedly raises public health concerns. In order to analyze the noise emission from wind turbines and to aid future wind energy development, a numerical simulation tool for the prediction of low-frequency noise and infrasound emission from wind turbines is developed. The simulation tool is a low-order model developed by combining aerodynamic noise theories and basic working principles of wind turbines. 2-D airfoil aerodynamics calculation is coupled with a subroutine that solves Ffowcs Williams-Hawkings (FW-H) equation in time domain. By omitting unsteady aeroacoustics mechanisms, the low-order simulation model is capable of computing infrasound emissions from multiple wind turbines simultaneously. By utilizing the low-order simulation model, the effects of wind directions, wind turbine locations, and phases of wind turbine rotations on the consequent aerodynamic infrasound are studied. Results of aerodynamic infrasound computation imply that wind farm configuration or wind turbine phase adjustment can help reduce the noise level at certain locations, which makes the low-order simulation model a useful tool to aid wind farm siting and controlling.

Infrasound- implications for human medicine

Infrasound describes ubiquitous, low-frequency sound (< 20 Hz) in the environment with along wavelength below the median hearing threshold, which can nevertheless be heard and tactilely perceived, depending on the sound pressure level and frequency spectrum. In nature, infrasound emissions usually occur only in the low-threshold range. Nevertheless, after strong and chronic exposure to usually artificially generated infrasound emissions, various effects on the ear and the body, sometimes questionably critical to health, can be observed. Correct measurement and assessment of infrasound sources is complex and controversial. Established guidelines are scarce. Innovative research areas include infrasound monitoring for evaluation of natural events and infrasound applications in medicine. In the future, it is hoped that new insights will be gained from infrasound research and that amore extensive classification in occupational medicine will be possible.

Comparison of infrasound emissions from tornadic and non-tornadic storms

At a previous ASA meeting (Spring 2019), some results corresponding to application of maximum likelihood estimation with the complex Wishart distribution to direction-of-arrival of infrasound from tornadic storms were presented. In this presentation, updated results are presented and compared with estimation of direction-of-arrival of infrasound from two non-tornadic storms that were measured with the same infrasound arrays. One of these storms was similar to the tornadic storm in that it consisted of numerous isolated storm cells with frequent lightning. The other storm was significantly different in that it was a well-organized squall line that produced only limited lightning. The tornadic storm yielded very well-defined direction-of-arrival tracks in contrast to the non-tornadic storms.

Wind turbine and infrasound: No evidence for health-related impairment - a physical, medical and social report

Based on the recent discussion about health impacts of wind turbine noise and infrasound emissions, we present the physical facts and summarize related studies in a narrative review. We are exposed to infrasound emissions from different sources, where wind turbine farms do not cause particularly high infrasound emissions. Epidemiological studies found no association between wind turbine farms and the incidence of diabetes mellitus, heart attacks, strokes and medication with antihypertensive drugs, but a more frequent prescription of sleep medication. In contrast, key indicators of objective sleep outcomes are not impacted by wind turbine noise. Health complaints are more frequently proven, if anti-wind-turbine-groups were active, which is consistent with the psychogenic hypotheses with nocebo effects likely play an important role. Without evidence of health impacts from wind turbine farms, an ongoing slowdown in the urgently needed expansion of renewable energies is not justifiable.

A Feasibility Study to Reduce Infrasound Emissions from Existing Wind Turbine Blades Using a Biomimetic Technique

Infrasound, i.e., low-frequency noise in the frequency range of 10–200 Hz, produced by rotating wind turbine blades has become a matter of concern because it is harmful to human health. Today, with the rapid increase of wind turbine size, this kind of noise is more worrying than ever. Although much effort has been made to design quiet wind turbine blades, today there is still a lack of effective techniques to reduce infrasound emissions from existing blades. To fill this gap in technology, a biomimetic technique that can be readily applied to reduce infrasound emissions of existing wind turbine blades is studied in this paper using both numerical simulation and experimental testing approaches. The numerical study of the technique is based on the analysis of the sound field distribution near the blade, which is derived by performing both aerodynamic and acoustic simulations of the blade. The experimental study of the technique is based on laboratory tests of two scale models of the blade. Both numerical and experimental studies have shown that the shedding vortices behind the blade can be successfully suppressed by semi-cylindrical rings wrapped on the blade. Consequently, both infrasound and the overall sound pressure level of the noise produced by the blade are significantly reduced. Although the rings fail to show good performance in reducing high-frequency noise, it is not a problem for human health because high-frequency noise is weak and moreover it attenuates rapidly as distance increases. The research also showed that the proposed technique can, not only reduce the infrasound produced by the blade, but can also improve the power coefficient of wind turbines.

Dust devils on Mars

Whirlwinds, familiar on Earth, can be informative probes of the Martian surface environment.

Infrasound and seismoacoustic signatures of the 28 September 2018 Sulawesi super-shear earthquake

Abstract. A magnitude 7.5 earthquake occurred on 28 September 2018 at 10:02:43 UTC near the city of Palu on the Indonesian island of Sulawesi. It was a shallow, strike-slip earthquake with a rupture extending to a length of about 150 km and reaching the surface. Moreover, this earthquake was identified as one of very few events having a super-shear rupture speed. Clear and long-lasting infrasound signatures related to this event were observed by four infrasound arrays of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organization as well as by one national infrasound station in Singapore. Although these infrasound stations SING (Singapore), I39PW (Palau), I07AU (Australia), I40PG (Papua New Guinea) and I30JP (Japan) are located at large distances of between 1800 and 4500 km from the earthquake's epicentral region, the observed infrasound signals associated with this event were intense, including both seismic and acoustic arrivals. A detailed study of the event-related infrasound observations and the potential infrasound generation mechanisms is presented, covering range-dependent infrasound transmission loss and propagation modeling and characterization of the atmospheric background conditions, as well as identification of the regions of seismoacoustic activity by applying a back-projection method from the infrasound receivers to potential source regions. This back projection of infrasonic arrivals allows one to estimate that the main infrasound source region for the Sulawesi earthquake is related to the extended rupture zone and the nearby topography. This estimation and a comparison to other super-shear as well as large regional earthquakes identify no clear connection between the earthquake's super-shear nature and the strong infrasound emission.

Comparison of infrasound emissions observed during a tornado with potential fluid mechanisms

Infrasound may be emitted by tornado-producing storms up to 2 h before tornadogenesis, and due to their low atmospheric attenuation, these low frequencies may be detected several hundreds of kilometers away. Therefore, passive infrasound monitoring shows potential for the study and prediction of tornadoes, provided received infrasound signals can be correlated with the flow-fields of tornadoes. Literature indicates that tornadoes do cause high infrasound levels between 0.5 Hz and 10 Hz, but the radially vibrating vortex mechanism commonly proposed to explain this production [Abdullah, Mon. Weather Rev. 94, 213–220] has been shown to be non-physical. Schecter [Mon. Weather Rev. 140, 2080–2089] showed these limitations and showed using numerical experiments of a tornado-like vortex produced infrasound from around the storm’s melting level. As this level contains diabatic processes involving hail, it also appears that hail production could be connected to tornado infrasound. In the current work, observations of atmospheric infrasound during a small tornado that occurred on 11 May 2017, will be evaluated in light of these previous studies.

Environmental Infrasound and Its Impact on Public Health in the Kashmir Region

In earlier published studies it was shown that an anomalous degree of human physiological ailments and a psychology of sustained anger and violence exist in highly populated countries located on boundaries of colliding Tectonic Plates in three continents at Latitude 34&#176 north. The Valley of Kashmir in Northern India is also located exactly on this latitude, hence chosen for detailed experimental verification of this phenomenon. This region also suffers from chronic public health hazards. Infrasound is very low frequency acoustic wave with frequencies ranging from 0.01 Hz to 20 Hz. It emanates from earthquakes, geological Faults, colliding tectonic plates and atmospheric wind turbulence. Hearing protections like ear muffs and ear plugs offer little protection. One single earthquake can cause multiple infrasound sources in a region. It is shown how regional geomorphology in the Kashmir Valley enhances and sustains this phenomenon. Both the percentage of population with hearing disabilities; and casualties due to social violence increase or decrease in proportion to frequency of earthquakes. Infrasound is shown to be the causal linkage. Public health hazards due to environmental infrasound closely resemble public health hazards actually being suffered by the population in Kashmir as established by formal and extensive medical investigations. Hence a Field Study was carried out to locate and record infrasound emissions in ten locations near 34&#176N latitude in Kashmir Valley. An analytical technique was developed to integrate infrasound spectrum in specific locations with public health hazards. It was discovered that infrasound recorded in South Kashmir around 34&#176N latitude at the locations of highest amplitude lies in proximity of Active Faults from earthquake ruptures; and in proximity to a large field of past earthquakes that took place in 2006-2012. A comprehensive public health security system needs to be set up very urgently. Technological measures are identified and appropriate technologies suggested cordoning off and mitigating this natural environmental hazard in the Kashmir Valley.

Simulated wind turbine emissions: Results from additional human response testing

Previous data (Nelson et al., ASA 2017) indicated that healthy human adult participants experienced few symptoms from re-created wind turbine sound and infrasound emissions. That report included more than fifty subjects ages 21–73 years who attended to audible and infrasound signals generated from a wind turbine, recorded at 300 meters and re-created in a laboratory. Stimuli consisted of modulated and unmodulated audible turbine sound at 50 dB SPL, as well as natural and peak-enhanced turbine infrasound at an overall level of approximately 85 dB SPL (peaks up to 100 dB SPL). Participants were tested for their postural stability, detection, and ratings of audible and infrasound emissions randomly presented in one-minute exposure intervals in the laboratory. Very few and minor adverse effects had been noted to date, mostly ear fullness or pressure. Healthy participants showed no evidence of any change in postural sway in the presence of infrasound for the group tested. We have recently begun testing of participants who either a) live near turbines and complain of adverse effects, or b) who have symptoms of dizziness/imbalance as reported to their ENT specialist. Results from postural sway, sound quality judgments, and pre- and post-exposure symptoms will be reported from some of these participants. [Work supported by Xcel Energy RDF14.]

A Study on the Correlation of Physiological and Psychological Health Hazards in Human Habitats with Seismicity, Mountain Air Turbulence and Environmental Infrasound

A statistical correlation study on the basis of published data has been performed in order to find whether an abnormal degree of human physiological ailments and a psychology of sustained violent reactions in highly populated habitats are correlated with environmental infrasound emissions related to seismic activity and sustained by mountain air turbulence. The study focus is on Latitude 34° North coinciding with boundaries of colliding Tectonic Plates in three continents. Earthquakes, rock fractures and landslides in these regions are creating geoacoustic activity in the form of hotspots of infrasound emissions. Sources of infrasound have been located by global infrasound monitoring stations. One single earthquake can cause multiple infrasound sources in a region. Low frequency “infrasound” creates an environment of unseen and inaudible energies that are hazardous to the local population. In one region on 34°N latitude the percentage of population with hearing disabilities increases or decreases almost directly proportional to frequency of earthquakes. In this region, the casualties due to social disorder and violence increased as the frequency of earthquake events increased and decreased as this frequency decreased. Comprehensive public health studies bring out that a sizable percentage of the regional population remain in a constant state of irritation, annoyance and anger; and suffer many other psychosomatic ailments corresponding to exposure to infrasound in 5 - 16 Hz frequencies and 120 - 140 dB amplitude. A new natural hazard inimical to life on planet earth has thus been identified. The time has arrived for public health authorities to locally pinpoint infrasound hotspots by scientific measurements. Thereafter new technologies can be developed to actively, and passively, mitigate/cancel these hazardous environmental emissions of infrasound and a Public Health Security Systems put in place as sustainable solutions for a healthy, livable habitat.

Human postural sway results in response to audible and infrasound emissions from wind turbines

Fifty healthy adult subjects ages 21–73 years attended to audible and infrasound signals generated from a wind turbine, recorded at 600 m and re-created in the laboratory. Stimuli consisted of modulated and unmodulated audible sound at 50 dB SPL, as well as recorded and peak-enhanced infrasound at an overall level of approximately 85 dB SPL (peaks up to 95 dB SPL). Participants were tested for their postural stability, detection, and ratings of audible and infrasound emissions from turbines. They also completed pre- and post-testing surveys for symptoms of imbalance. All subjects were blind to the knowledge that the stimuli were recorded from wind turbines. No significant adverse effects from healthy adults have been noted to date. Some individuals reliably indicated detection of infrasound signals. A few participants indicated mild symptoms (a rating of 1 on a scale from 0 to 4) following the test. Testing of patients who report vertigo will begin soon. Detailed results and implications will be discussed.

Measures of sway as perceptual response to infrasound

Some reports suggest possible negative human perceptual responses to infrasound and audible noise from wind turbines. Recordings were made in the field of turbine noise (audible and infrasound) at 300 meters. In our multisensory laboratory (Center for Applied and Translational Sensory Science at the University of Minnesota) we are re-creating these natural stimuli in a controlled environment. Infrasound stimuli were presented at approximately 85 dB SPL; audible stimuli were 55 dB SPL. Stimulus configurations were combinations of audible and infrasound emissions, testing the effects of these stimuli individually and in combination. We measured sway using an AMTI AccuSway Optimized force plate. Preliminary data suggest that measures of sway are stable and reproducible, and that some persons may show changes in stance in the presence of combinations of audible and infrasound stimuli. [Funding provided by Xcel Energy RD-14 to the University of Minnesota.]

Infrasound emission of the Chelyabinsk meteoroid

Data from observing the infrasound effects induced by the Chelyabinsk meteoroid impact of February 15, 2013 are presented. Similar infrasound effects registered earlier and ways of interpreting them are described. The characteristics of the infrasound station of the Institute of Solar and Terrestrial Physics, Russian Academy of Sciences, Siberian Branch, Irkutsk, which registered the effect of the meteoroid explosion in the atmosphere, are also described. The shape of the infrasound signal from the Chelyabinsk meteoroid is presented and its parameters are discussed.

Detection of volcanic infrasound with a ring laser interferometer

Over the last 15 years, large horizontally mounted ring lasers have been used to study numerous geophysical phenomena. This paper provides examples of the sensitivity of large active ring laser interferometers to far field infrasound emissions from explosive volcanic eruptions. Volcanic infrasound is reported from representative eruptions of volcanoes Kelut (Kelud), Klyuchevskaya (Kliuchevskoi), Puyehua, Santa Maria, Sakurajima, and Tungurahua. The detected infrasound frequencies are in basic agreement with the far field air wave frequencies from the 1980 eruption of Mount St. Helens and the 1991 eruption of Mount Pinatubo. Cavities of large horizontally mounted active ring lasers contain two counter-propagating waves that in the presence Earth's rotation become traveling waves of slightly different frequencies. The Sagnac or beat frequency due to the difference in the traveling wave frequencies is modulated by geophysical phenomena, in this case volcanic infrasound. Signatures of the infrasound are found in the frequency modulated side bands.

Experimental modeling of infrasound emission from slug bursting on volcanoes

AbstractThe acoustic signal produced by gas slugs bursting at volcano vents is investigated by means of laboratory experiments. In order to explore the transition between linear and nonlinear acoustics, we model the bubble by an overpressurized cylindrical cavity closed by a membrane. We find that the acoustic waveform inside and outside the cavity, produced by the membrane bursting, is well described by the linear acoustics equations and a monopole source model up to an initial overpressure inside the cavity of about 24 kPa. For higher overpressure, the amplitude inside the conduit is smaller than the linear prediction, whereas the amplitude measured outside is larger. The frequency content remains harmonic, even at high initial overpressure. Changing the bursting depth in the conduit does not change the scaling of the amplitudes but affects the waveform and energy partitioning. We show that the energy of the first signal period is about 30% of the total acoustic energy and can be used as a good estimate, with a geometrical correction to account for the bursting depth.

The Effect of Wind Turbine Infrasound Emission on Subjectively Rated Activation Level

The problem of low-frequency acoustic waves emitted by wind turbine farms has become a great challenge to acousticians in Europe for more than 20 years. In Poland wind farm industry is growing rapidly and generates questions about the in uence of such sounds on human organism. A short survey of previously published reports concerning subjectively perceived in uence of wind turbines on people living next to wind farms is given together with the results of the Thayer's test measuring the di erence in activation level before and after exposition on infrasound wave generated by a wind turbine. Statistically signi cant increase of the High Activation Level representing a tension type arousal has been revealed.

Infrasound Sensitizes Human Glioblastoma Cells to Cisplatin-Induced Apoptosis

The development of nontoxic agents that can selectively enhance the cytotoxicity of chemotherapy is an important aim in oncology. This study evaluates the ability of infrasound exposure to sensitize glioblastoma cells to cisplatin-induced apoptosis. The infrasound was delivered using a device designed to replicate the unique infrasound emissions measured during external Qigong treatments. Human glioblastoma cell lines harboring wild-type p53 (U87) or mutant p53 (U251, SF210, and SF188) were treated in culture with cisplatin, infrasound emissions, or the combination of the 2 agents. Induction of apoptosis was quantified after 24 hours by flow cytometry following annexin V/propidium iodide staining. Infrasound emissions alone, delivered at moderate levels (~10 mPa) with dynamic frequency content (7-13 Hz), did not induce apoptosis, yet combining infrasound with cisplatin augmented the induction of apoptosis by cisplatin in all the 4 cell lines (P < .05). Increased cellular uptake of the fluorophore calcein associated with infrasound exposure was quantified by fluorescence microscopy as well as flow cytometry, demonstrating increased cell membrane permeability. The 4 cell lines differed in the degree to which infrasound exposure increased calcein uptake, and these differences were predictive of the extent to which infrasound enhanced cisplatin-induced apoptosis. When exposed to specific frequencies, membrane permeabilization also appeared to be differentially responsive for each cell line, suggesting the potential for selective targeting of tissue types using isolated infrasonic frequencies. Additionally, the pressure amplitudes used in this study were several orders of magnitude less than those used in similar studies involving ultrasound and shock waves. The results of this study provide support for using infrasound to enhance the chemotherapeutic effects of cisplatin in a clinical setting.

Application of a blind source separation algorithm for the detection and tracking of tornado-generated infrasound emissions during the severe weather outbreak of 27 April 2011

April 25-28, 2011 has been identified by many as the most significant and severe single-system outbreak of tornadoes in recorded history. One day in particular, the 27th of April, has been classified by the National Oceanic and Atmospheric Administration (NOAA) as the fourth deadliest tornado outbreak in US history. Severe tornadic activity on this day levied catastrophic damage to life and property across areas of Mississippi, Alabama, Georgia and Tennessee. During this outbreak, multiple Ducommun Miltec-developed infrasound sensors collecting continuous, high resolution data were deployed in two-dimensional array configurations in Northern Alabama. Prior research on the collection and analysis of infrasonic emissions from severe weather phenomenon has provided much insight on the nature of tornado-generated infrasound. Our effort focuses on the application of novel bearing estimation algorithms using closely spaced (4-6 m) array elements. Direction of Arrival (DOA) estimates, derived from Blind Source Separation (BSS) techniques, will be presented for at least two significant tornadoes: the long-track EF5 that impacted Hackleburg and Phil Campbell, AL and the large multi-vortex EF4 that struck Cullman, AL. Correlation of infrasound detection and bearing estimate initiation and termination with NOAA Storm Prediction Center (SPC) Storm Reports will also be reviewed.

Test Research on Infrasound Wave of Granite Damage Course under Dynamic Uniaxial Compression

More and more engineers apply AE (Acoustic Emission) to research rock fracture and damage. Infrasonic wave could be used to forecast earthquake, and structure earthquake is almost caused by rock compression damage, so in the course of rock fracture and damage, the infrasound wave emission could be researched in order to forecast earthquake. The granite specimens are compressed to damage. The infrasonic information in the course of compression are detected and collected. By means of data analysis, some principles of rock compression damage are found.