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Infrasound

Infrasound encompasses acoustic waves with frequencies below the lower limit of human audibility, typically ranging from 0.001 Hz to 20 Hz.^[1]^[2] These low-frequency sounds are inaudible to the human ear under normal conditions but can produce perceptible vibrations at sufficiently high amplitudes, often exceeding 100–110 dB.^[3]^[4] Infrasound is generated by diverse natural and anthropogenic sources, including explosive volcanic eruptions, earthquakes, severe weather phenomena such as tornadoes, ocean waves, auroras, and animal vocalizations, as well as human-induced events like nuclear detonations, rocket launches, and industrial activities including wind turbines.^[5]^[6]^[7]^[8]^[9] A key property of infrasound is its ability to propagate over vast distances—often thousands of kilometers—due to reduced atmospheric absorption at lower frequencies compared to higher ones, enabling global-scale detection.^[10]^[11] This long-range travel is influenced by atmospheric conditions, including wind and temperature gradients, which can refract and duct the waves.^[12] Applications of infrasound monitoring are extensive in geophysics and environmental science, including the verification of the Comprehensive Nuclear-Test-Ban Treaty through the International Monitoring System, real-time detection of volcanic activity and avalanches, and assessment of atmospheric events like meteors or wildfires.^[5]^[13]^[14] In aviation and meteorology, specialized infrasound sensors detect clear air turbulence, aircraft wake vortices, and severe storms from afar, enhancing safety and forecasting.^[1]^[15] Maritime and terrestrial arrays further support ocean monitoring and seismic event localization.^[16] Regarding biological impacts, high-intensity infrasound (above 100 dB) has been linked to physiological effects in humans, such as reduced myocardial contractility and potential interference with vestibular and cardiovascular systems after short exposures.^[9]^[17] Conversely, controlled low-level exposure may promote tissue healing, including enhanced bone growth and wound repair in some studies.^[18] In the animal kingdom, infrasound plays a vital role in communication; elephants, for instance, produce and detect infrasonic rumbles to coordinate over kilometers, while whales use similar frequencies for underwater signaling.^[8]^[19]

Definition and Fundamentals

Definition

Infrasound encompasses acoustic waves with frequencies below the lower threshold of human audibility, typically defined as ranging from 0.001 Hz to 20 Hz. This places it distinctly below the audible sound spectrum, which begins at approximately 20 Hz for most individuals under standard conditions. The upper limit aligns with the human hearing threshold as established by acoustic standards, while the lower bound extends into ultra-low frequencies relevant for atmospheric and geophysical monitoring.^[20]^[21] The term infrasound is sometimes interchangeably used with "low-frequency sound" or "subsonic acoustic waves," reflecting its position in the broader acoustic continuum. However, "subsonic" properly denotes propagation speeds slower than the speed of sound, a distinction from frequency-based classification, to avoid conflating wave velocity with oscillatory rate. This nomenclature emphasizes infrasound's role as an extension of audible acoustics into imperceptible realms.^[22]^[23] Physically, infrasound manifests as longitudinal pressure oscillations in elastic media, such as the atmosphere, oceans, or earth's crust, propagating as mechanical waves. Given the speed of sound in air (approximately 343 m/s), these waves exhibit correspondingly long wavelengths—from about 17 meters at 20 Hz to over 300 kilometers at 0.001 Hz—enabling extensive travel with minimal attenuation in certain environments.^[23]^[24] Measurement of infrasound intensity relies on sound pressure, quantified in pascals (Pa) for absolute values or in decibels (dB) on a logarithmic scale relative to a standard reference pressure of 20 micropascals (20 μPa) in air. This reference corresponds to the nominal threshold of human hearing at 1 kHz, providing a consistent basis for comparing infrasonic amplitudes across studies and applications.^[25]^[26]

Physical Characteristics

Infrasound consists of acoustic waves with frequencies typically ranging from 0.001 Hz to 20 Hz, resulting in extremely long wavelengths that distinguish them from audible sound. At the upper frequency limit of 20 Hz, the wavelength is approximately 17 meters, calculated as the speed of sound in air divided by the frequency (λ = c/f, where c ≈ 343 m/s at 20°C). At the lower end, near 0.001 Hz, wavelengths extend to about 343 kilometers, though practical ranges often cite 170 kilometers for slightly higher frequencies around 0.002 Hz under standard atmospheric conditions.^[27]^[28] The propagation speed of infrasound in air is the speed of sound, approximately 343 m/s, but it varies with temperature (increasing by about 0.6 m/s per °C) and wind velocity, which can add or subtract up to tens of m/s in the direction of travel.^[29] These long wavelengths contribute to low attenuation rates in the atmosphere, where absorption is minimal due to reduced molecular relaxation and viscosity effects at low frequencies. For instance, classical attenuation is on the order of 0.03 dB per 1000 km at 1 Hz, dropping even lower at infrasonic frequencies, which allows signals to travel globally with little energy loss from dissipation.^[30] Refraction plays a key role in long-range propagation, as infrasound waves bend according to Snell's law when encountering atmospheric layers with varying sound speeds; in the troposphere, decreasing temperatures cause upward refraction, while the warmer stratosphere enables ducting that channels waves over thousands of kilometers.^[31] Overall absorption remains below 1 dB/km even at 1 Hz under typical conditions, far lower than for audible frequencies.^[32] Infrasound interacts with various media through transmission, reflection, and diffraction, facilitated by its extended wavelengths that minimize scattering. These waves transmit efficiently across boundaries between gases, liquids, and solids, with transmission coefficients depending on acoustic impedance mismatches; for example, at gas-solid interfaces, shear rigidity can enhance reflection, but low-frequency content ensures partial transmission into the solid.^[33] Long wavelengths promote diffraction around obstacles, allowing infrasound to bypass barriers that would block higher-frequency sound, and reflections occur at surfaces with impedance contrasts, such as ground-air interfaces during seismic events.^[34] The energy and intensity of infrasound follow the inverse square law for spherical spreading in free space (intensity I ∝ 1/r², where r is distance), but this effect is mitigated over long ranges by atmospheric waveguides that concentrate energy, making geometric spreading less dominant than for audible sound. Amplitudes scale with event magnitude; for instance, large quakes (M > 7) can produce signals exceeding 10 Pa at regional distances after propagation.^[35]^[36]

Historical Development

Early Discoveries

The earliest documented observation of infrasound dates to the 19th century, when the catastrophic 1883 eruption of Krakatoa in Indonesia generated global atmospheric pressure waves recorded on barometers as far away as 16,000 km. These waves, with frequencies below 20 Hz, circled the Earth up to four times, marking the first unintentional detection of infrasound propagation, though not recognized as such until later analyses.^[24] Concurrently, early seismologists noted low-frequency vibrations associated with earthquakes, using rudimentary instruments like seismoscopes to capture ground motions that included infrasonic components, often without distinguishing them from purely seismic activity.^[37] During World War I (1914–1918), military acoustics advanced through efforts to locate enemy artillery, incorporating seismic ranging techniques that detected ground vibrations from shell impacts and gun fire—vibrations in the infrasonic range transmitted through soil and rock. British and French forces deployed geophones and early seismometers in trench warfare to triangulate positions based on these low-frequency signals, achieving accuracies within hundreds of meters despite challenges from wind and terrain.^[38] World War II saw similar innovations for bomb and artillery detection, with Allied and Axis engineers refining vibration sensors to monitor distant explosions, laying groundwork for postwar acoustic monitoring systems. In the post-World War II era, systematic recognition of infrasound emerged in the late 1940s through oceanographic studies led by geophysicist Maurice Ewing, who documented atmospheric low-frequency sounds during expeditions, highlighting their propagation via refractive layers similar to the ocean's SOFAR channel discovered in 1944.^[39] By the 1950s, amid Cold War tensions, both the United States and Soviet Union invested in infrasound research to detect nuclear blast waves, establishing monitoring arrays that captured long-range signals from atmospheric tests, with frequencies as low as 0.1 Hz traveling thousands of kilometers.^[40] These efforts revealed initial misconceptions, as infrasonic arrivals were frequently conflated with seismic waves on shared instruments, leading to erroneous source attributions until acoustic-seismic separation techniques developed in the early 1960s clarified their distinct propagation paths.^[41]

Modern Advancements

The field of infrasound research solidified in the 1960s and 1970s through U.S. military and civilian initiatives aimed at monitoring atmospheric nuclear explosions and natural phenomena. The U.S. Air Force spearheaded early efforts, deploying infrasound arrays to detect distant blasts as part of Cold War-era defense programs, which laid the groundwork for systematic atmospheric acoustics studies.^[42] Concurrently, the National Oceanic and Atmospheric Administration (NOAA) advanced the discipline via projects at its Physical Sciences Division, inventing sensitive microbarometers in the 1970s and 1980s to capture low-frequency pressure waves for monitoring events like tornadoes and avalanches.^[43] These instruments, with their high sensitivity to signals below 20 Hz, enabled the first global-scale atmospheric propagation models and noise reduction techniques, establishing infrasound as a viable tool for environmental surveillance.^[44] A pivotal milestone came with the 1996 Comprehensive Nuclear-Test-Ban Treaty (CTBT), which catalyzed international collaboration and infrastructure development. The treaty's verification regime prompted the creation of the International Monitoring System (IMS), a global network incorporating 60 infrasound stations designed to detect nuclear detonations and other impulsive events through long-range acoustic propagation.^[45] By 2025, the IMS had achieved near-full operational certification for its infrasound component, with stations spaced approximately every 2,000–3,000 km to provide comprehensive hemispheric coverage and real-time data sharing among member states.^[45] This network not only enhanced nuclear non-proliferation efforts but also opened avenues for civilian applications, such as tracking volcanic eruptions and meteor impacts. Post-2010 advancements have focused on sophisticated signal processing to improve event localization and discrimination amid ambient noise. Techniques like robust regression estimators and narrow-band least-squares methods have refined beamforming algorithms in infrasound arrays, enabling precise back-azimuth estimation and yield calculations for sources up to thousands of kilometers away with errors reduced to under 1–2 degrees.^[46]^[47] Recent studies, including those from 2025, have explored infrasound's role in earthquake early warning systems, where seismoacoustic coupling allows detection of precursor waves for tsunami alerts in regions like the eastern Mediterranean.^[48] Similarly, correlations between auroral electrojet arcs and infrasound signals—observed at frequencies below 0.1 Hz—have advanced climate and ionospheric monitoring, linking geomagnetic activity to atmospheric dynamics in polar regions.^[49] Key milestones include the 1990s investigations by researcher M. J. Heavner, whose work during the Sprites '94 campaign documented infrasonic signatures from upper-atmospheric electrical discharges, bridging thunderstorm acoustics with transient luminous events.^[50] More recently, integration of infrasound data with satellite observations has revolutionized meteor detection; for instance, Geostationary Lightning Mapper (GLM) imagery from GOES satellites has been cross-correlated with ground-based arrays to characterize fireball energies and trajectories, as demonstrated in analyses of events from 2018–2023.^[51] By 2025, such hybrid approaches have enabled more accurate estimates for bolide impacts, underscoring infrasound's growing synergy with space-based assets.

Generation and Sources

Natural Sources

Infrasound arises from various geophysical processes, including earthquakes, which generate low-frequency acoustic waves primarily through the propagation of P-waves in the frequency range of 0.01 to 1 Hz.^[52] Volcanic eruptions produce impulsive infrasound signals, often in pulses between 0.5 and 5 Hz, resulting from explosive gas releases, rockfalls, and lava movements.^[53] Landslides and avalanches also contribute significantly, with large mass-wasting events creating broadband infrasound from the rapid displacement of material, detectable at distances up to hundreds of kilometers.^[54] Atmospheric phenomena serve as prominent natural generators of infrasound. Meteor airbursts produce signals in the 0.1 to 10 Hz range due to shock waves from atmospheric entry and explosion.^[44] Severe weather events, such as tornadoes, emit infrasound from vortex motion and pressure fluctuations, typically in the 1 to 20 Hz band, allowing detection far from the storm.^[55] Auroral activity in the polar atmosphere generates infrasound below 1 Hz through upper atmospheric disturbances from charged particle interactions.^[41]^[56] Oceanic sources include microbaroms, continuous infrasound waves in the 0.1 to 0.5 Hz range originating from nonlinear interactions between opposing ocean surface waves.^[57] Underwater volcanic activity contributes through eruptions and hydrothermal processes, producing low-frequency signals similar to subaerial volcanoes but coupled with the water column.^[58] Certain marine mammals, such as whales, incorporate infrasonic components (10 to 20 Hz) into their songs, enabling long-distance communication across ocean basins.^[59] Biological origins of infrasound are evident in large terrestrial animals. African elephants produce rumbles with fundamental frequencies of 14 to 35 Hz, including infrasonic components below 20 Hz that propagate over several kilometers for social coordination and long-range signaling.^[60] Tigers generate low-frequency roars and growls extending into the infrasonic range, aiding in territory marking and intimidation over distances.^[61]

Anthropogenic Sources

Anthropogenic sources of infrasound encompass a wide array of human activities, particularly those involving high-energy releases or mechanical operations that generate low-frequency acoustic waves below 20 Hz. These sources contrast with natural phenomena by being tied to engineered processes, often producing broadband signals that propagate over long distances due to their low attenuation in the atmosphere.^[20] Military and explosive activities represent prominent generators of infrasound. Nuclear tests, both atmospheric and shallow underground, produce broadband signals spanning 0.01 to 50 Hz, detectable globally by monitoring networks due to their impulsive nature and high energy.^[20] Conventional blasts, such as those from artillery or demolition, similarly emit infrasonic pulses in the 0.1 to 20 Hz range, with amplitudes that can exceed 100 dB near the source.^[58] Rocket launches contribute significant infrasound through lift-off vibrations and sonic booms, particularly in the 1 to 10 Hz band, where exhaust plumes and shock waves create sustained rumbles detectable thousands of kilometers away.^[62] For instance, Falcon 9 launches have been recorded with peak pressures corresponding to infrasonic signals propagating via atmospheric ducting.^[63] Industrial operations are another major category, often producing continuous or periodic infrasound from mechanical interactions. Wind turbines generate infrasound primarily through blade passage modulation at frequencies of 0.5 to 10 Hz, with levels reaching 60 to 80 dB at 100 meters from the source under full load conditions.^[64] Heavy machinery, including pumps, compressors, and air handlers in factories, emits persistent low-frequency hums in the 1 to 20 Hz range, arising from rotational imbalances and fluid dynamics.^[65] Aircraft operations, especially supersonic flights, produce sonic booms with infrasonic tails below 10 Hz, while subsonic takeoffs generate peaks from engine thrust and airframe vibrations.^[66] Urban traffic, encompassing heavy vehicles and rail systems, contributes background infrasound around 5 to 20 Hz from tire-road interactions and engine cycles.^[58] Other human activities include mining explosions and large-scale events. Blasts in open-pit mining yield impulsive infrasound signals with dominant frequencies of 0.5 to 5 Hz, similar in character to military detonations but scaled to charge size, often monitored for seismic-infrasonic correlation.^[67] Chemical processing plants produce ongoing infrasonic emissions from reactors and distillation columns, typically in the 2 to 15 Hz band due to turbulent flows and vibrations.^[65] Concerts and public events with powerful subwoofers can generate transient infrasound down to 10 Hz, though at lower amplitudes than industrial sources.^[58]

Propagation and Detection

Propagation Mechanisms

Infrasound propagates through the atmosphere primarily via refraction and ducting mechanisms influenced by temperature and wind gradients. In the troposphere, ducting occurs within inversion layers where sound speed increases with height, trapping waves and enabling ranges up to several hundred kilometers; stratospheric shadows, conversely, arise from upward refraction in warmer upper layers, creating zones of reduced detection beyond 100-200 km from the source.^[68] Seasonal variations significantly affect these paths, with winter conditions in the Northern Hemisphere promoting longer propagation distances—often exceeding 1000 km—due to eastward stratospheric winds that enhance ducting efficiency, while summer westward winds limit ranges to under 500 km.^[69] These low-frequency physical properties, such as minimal classical absorption below 10 Hz, further facilitate efficient long-distance travel with limited energy loss.^[10] Ground coupling allows infrasound to transition between media, particularly at soil-air interfaces where seismic waves from subsurface sources convert to acoustic waves, with efficiency depending on soil porosity and impedance mismatch; this process typically attenuates higher frequencies more rapidly, preserving infrasonic components for atmospheric propagation.^[70] For underwater sources, such as oceanic disturbances, energy couples into the atmosphere via surface waves, where hydroacoustic-to-acoustic conversion occurs at the air-water boundary, enabling detection of marine events over continental distances.^[69] On a global scale, zonal winds in the stratosphere and mesosphere guide infrasound circumnavigation of the Earth, with multipath arrivals resulting from reflections off the ionosphere and repeated stratospheric ducting, leading to signal arrivals separated by hours at antipodal stations. These paths can span thousands of kilometers, as evidenced by volcanic eruptions detected over 1000 km via stratospheric propagation.^[71] Attenuation of infrasound is dominated by scattering from atmospheric turbulence, which disrupts coherence over irregular paths, and classical absorption, which is minimal below 10 Hz and weakly dependent on humidity due to reduced molecular relaxation effects at low frequencies.^[72] Viscosity-induced damping provides additional but minor losses, allowing signals to retain detectable amplitudes after traversing 1000 km or more under favorable conditions.^[73]

Measurement Techniques

Infrasound measurement relies primarily on specialized sensors designed to detect subtle atmospheric pressure fluctuations in the infrasonic frequency band, typically below 20 Hz. Microbarometers are the most commonly used instruments, functioning as absolute pressure sensors that convert pressure changes into electrical signals with high sensitivity. For instance, the CEA MB2000 microbarometer, developed by the French Atomic Energy Commission, exhibits a nominal sensitivity of approximately 20 mV/Pa and can resolve pressure variations as low as 1 mPa or better, with instrumental noise less than 2 mPa in the 0.02-4 Hz band, enabling detection of weak signals from distant sources.^[74] Similarly, the Chaparral Physics Model 5 microbarometer achieves a sensitivity around 100 mV/Pa while minimizing interference from regional barometric pressure changes through a compact design with reduced backing volume and controlled leaks. These sensors operate effectively from about 0.02 Hz to 20 Hz, though their lower frequency limit can extend to 0.001 Hz under optimal conditions, allowing capture of ultra-low-frequency waves. Infrasound microphones, often integrated with microbarometers, further enhance detection by incorporating wind noise reduction features essential for outdoor deployments. Wind noise, generated by turbulent airflow, can overwhelm infrasonic signals, so these microphones employ passive spatial filters such as rosette pipe arrays—networks of interconnected pipes that average pressure inputs across multiple inlets to suppress turbulence-induced fluctuations while preserving coherent infrasound. For example, systems using four to six 20-foot pipe lengths as windscreens have demonstrated significant noise attenuation above 0.5 Hz, with reductions up to 20-30 dB in turbulent conditions. These configurations are standard in field measurements, balancing signal fidelity with environmental robustness. To improve signal localization and discrimination, infrasound detection often employs spatial arrays of multiple sensors arranged in geometric patterns, such as triangles or crosses, for beamforming and direction-finding techniques. Typical arrays consist of 4 to 9 microbarometers spaced 1 to 2 km apart, creating apertures of 1 to 4 km that exploit phase differences in arriving wavefronts to estimate source azimuth and trace velocity. This setup enhances signal-to-noise ratios by coherently summing signals from the direction of interest while nulling noise from other angles. On a global scale, the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) comprises 60 planned infrasound stations, with 53 certified as of 2025, including primary and auxiliary sites, distributed worldwide to form a networked monitoring array with apertures ranging from 1 to 3 km. These networks enable triangulation of events across continents, achieving detection thresholds around 1 mPa for impulsive sources, consistent with sensor noise levels. Data processing for infrasound signals involves advanced techniques to extract meaningful information from raw pressure time series. The Fourier transform, particularly the fast Fourier transform (FFT) or short-time Fourier transform (STFT), is fundamental for frequency-domain analysis, decomposing signals into spectral components to identify dominant infrasonic frequencies and filter out higher-frequency noise. For event discrimination, signal correlation methods compute time delays between array sensors, quantifying coherence to distinguish coherent propagating waves from local noise or multipath arrivals. A widely adopted algorithm is the Progressive Multi-Channel Correlation (PMCC), which iteratively builds correlation matrices across subsets of array channels to detect and parameterize multipath arrivals, achieving robust performance even in low-signal environments with back azimuth resolution better than 1 degree. PMCC has been optimized for IMS data, reducing false alarms by incorporating progressive slowness grids that model expected wave speeds. Calibration of infrasound systems ensures accuracy across their operational range, typically from 0.001 Hz to 50 Hz, with sensitivity calibrated using traceable sources like pistonphones or explosive references to achieve uncertainties below 1 dB. Challenges include wind noise mitigation, addressed through spatial filtering in arrays, which can reduce turbulent noise by 10-40 dB via differential processing that cancels uncorrelated fluctuations. However, limits persist at very low frequencies (<0.01 Hz), where long-period barometric variations dominate, necessitating site selection in sheltered locations or advanced adaptive filtering to maintain detection thresholds around 1 mPa.

Biological Impacts

Effects on Animals

Infrasound plays a crucial role in animal communication, enabling long-distance signaling in species adapted to low-frequency sound propagation. African elephants (Loxodonta africana) produce rumbles in the 15-35 Hz range, with sound pressure levels reaching 117 dB, allowing coordination of group movements and location of mates over distances up to 10 km through atmospheric and ground channels. Baleen whales, such as blue whales (Balaenoptera musculus), emit songs with fundamental frequencies of 10-20 Hz that travel thousands of kilometers in water, facilitating migration coordination and social bonding across ocean basins.^[75] Certain birds, including homing pigeons (Columba livia), detect infrasound from 0.5-10 Hz to form acoustic maps of geographic features like ocean shorelines, aiding navigation over vast distances.^[76] Animals exhibit varied behavioral responses to infrasound, often involving avoidance to evade threats. Juvenile salmonids, such as chinook salmon (Oncorhynchus tshawytscha), display flight or avoidance behaviors when exposed to 10 Hz pulses, demonstrating sensitivity to particle motion in water that triggers escape reactions. Anthropogenic infrasound from naval sonar disrupts marine mammals, causing beaked whales (family Ziphiidae) to alter diving patterns, cease foraging, and in extreme cases, strand en masse, as observed in events correlated with mid- and low-frequency active sonar exercises.^[77] Physiological effects of infrasound include stress responses that can impair health and survival. In Wistar rats, exposure to infrasound below 20 Hz at 120 dB induces coronary perivascular fibrosis, a cardiovascular change potentially linked to inflammatory mechanisms.^[78] For whales, intense naval infrasound contributes to decompression-like injuries and disorientation, potentially underlying mass strandings where affected individuals exhibit gas bubble lesions in tissues.^[79] Tigers (Panthera tigris) incorporate infrasonic components (below 20 Hz) in their roars to mark territory and intimidate rivals over several kilometers, leveraging low-frequency propagation through vegetation.^[61] Evolutionary adaptations in elephants include trunk-based receptors sensitive to infrasound vibrations, enhancing reception of distant calls alongside foot pads for seismic detection, which supports social cohesion in herds.^[80]

Effects on Humans

Infrasound exposure at high intensities exceeding 140 dB can induce physiological responses in humans, including nausea, headaches, and vestibular disturbances such as dizziness and disorientation.^[81] These effects arise from the interaction of intense low-frequency vibrations with the body's sensory systems, particularly the inner ear's vestibular apparatus, leading to sensations of pressure and imbalance.^[82] However, no definitive evidence supports long-term harm from infrasound below 100 dB, though chronic low-level exposure in the 50-70 dB range, such as from wind turbines, has been associated with symptoms like fatigue, irritability, and sleep disturbances due to autonomic nervous system imbalances.^[83] Psychological effects of infrasound often manifest as subtle unease or sensations of being "haunted," particularly at frequencies around 18-19 Hz, which resonate with the human eyeball and can cause visual distortions or anxiety.^[84] In a seminal 1998 study, engineer Vic Tandy demonstrated that a 19 Hz standing wave in a laboratory environment produced ghostly apparitions and feelings of dread by inducing eyeball vibrations and physiological discomfort.^[85] Similarly, a 2003 experiment exposing concert attendees to a concealed 17 Hz tone reported no significant auditory perception but induced subtle anxiety, chills, and revulsion in about 22% of participants.^[86] The popular myth of the "brown note"—an infrasonic frequency purportedly causing involuntary bowel movements—lacks scientific support and has been debunked through physiological testing, as no such resonant effect on the human digestive system has been observed.^[87] Regulatory standards aim to mitigate potential risks from occupational infrasound exposure. The Danish Environmental Protection Agency's 1997 guidelines recommend indoor infrasound levels not exceeding 85 dB(G) to prevent annoyance and stress.^[88] In the European Union, occupational exposure directives (e.g., 2003/10/EC) incorporate low-frequency noise considerations through C-weighting for peak levels, with general exposure action values at 80-85 dB(A) to protect against vibration-induced fatigue and discomfort in industrial settings.^[89] The International Organization for Standardization (ISO 7196) provides G-weighting for infrasound measurement; some national standards recommend occupational limits of 100-110 dB(G) for an 8-hour workday using this weighting to safeguard vestibular and cardiovascular health.

Applications and Uses

Monitoring and Surveillance

Infrasound monitoring plays a critical role in nuclear arms control through the Comprehensive Nuclear-Test-Ban Treaty Organization's (CTBTO) International Monitoring System (IMS), a global network of 60 infrasound stations designed to detect atmospheric disturbances from nuclear explosions. The IMS has successfully identified all six of North Korea's declared nuclear tests between 2006 and 2017, including the September 2017 event, where infrasound signals confirmed the explosion's occurrence and contributed to locating the site with an accuracy of approximately 10 km when integrated with seismic data.^[45]^[90]^[91] For natural disaster tracking, infrasound arrays enable long-range detection of volcanic eruptions, such as the 2022 Hunga Tonga-Hunga Ha'apai event, whose acoustic waves were recorded over 10,000 km away by stations worldwide, providing insights into eruption dynamics and atmospheric propagation. Infrasound also aids earthquake monitoring by capturing precursors—low-frequency signals generated by crustal stress—that can precede seismic shaking by days in some cases, allowing for potential early alerts. Additionally, infrasound sensors detect tsunami-generating events through air-sea coupling, where ocean waves produce detectable low-frequency pressure changes that propagate faster than the water waves themselves, enhancing warning systems in coastal regions.^[92]^[93]^[94] In wildlife and climate monitoring, infrasound facilitates non-invasive tracking of animal movements and weather phenomena; for instance, arrays capture elephant rumbles, which travel several kilometers and reveal migration patterns and social behaviors in savanna ecosystems. Storm systems, including hurricanes and tornadoes, generate characteristic infrasound signatures in the 2-6 Hz range, enabling remote assessment of convective activity over hundreds of kilometers. Advancements in infrasound networks have improved real-time meteorite detection, enabling faster processing of global events like fireballs.^[95]^[96]^[97] Forensic applications leverage infrasound waveform analysis to differentiate man-made blasts from natural earthquakes; quarry explosions produce distinct high-amplitude, short-duration signals compared to the prolonged, lower-frequency oscillations from tectonic events, aiding in event discrimination with seismo-acoustic data. In border surveillance, portable infrasound arrays detect illicit explosions, such as those from mining or smuggling operations, by identifying impulsive low-frequency arrivals that distinguish them from ambient noise, supporting rapid response in remote areas.^[98]^[99]^[100]

Medical and Therapeutic

Infrasound has shown emerging potential in medical diagnostics through the detection of low-frequency vibrations generated by vital organs. In-ear infrasonic hemodynography, for instance, captures acoustic waveforms from vibrations below 20 Hz produced by cardiovascular and respiratory activities, enabling non-invasive assessment of hemodynamic parameters that could aid in identifying abnormalities in lung function or related conditions.^[101] Therapeutic applications of infrasound focus on its ability to stimulate cellular processes and promote tissue repair. A 2025 systematic review analyzed studies on infrasound frequencies between 1-20 Hz, finding that controlled exposure accelerates wound healing by enhancing fibroblast proliferation, collagen synthesis, and angiogenesis through mechanotransduction pathways that activate cellular signaling.^[102] In physiotherapy, pulsed infrasound at around 10 Hz has been employed to alleviate musculoskeletal pain by modulating nociceptor activity and improving local blood flow, with reports of reduced inflammation in chronic conditions after short sessions.^[103] These effects stem from infrasound's capacity to induce subtle vibrations that mimic natural physiological oscillations, fostering repair without invasive intervention.^[104] Neurological uses of infrasound target vestibular and brain modulation to address disorders like anxiety and Parkinson's disease. These applications draw on the overlap between infrasound frequencies and endogenous brain rhythms, potentially offering non-pharmacological adjunct therapy.^[105] Safety in medical infrasound applications requires strict adherence to exposure guidelines to prevent adverse effects. Recommended limits include sound pressure levels below 120 dB for durations up to 30 minutes, as higher intensities can disrupt cardiac or vestibular function, while general population thresholds are set at 100 dB to avoid annoyance or physiological stress.^[106] Ongoing clinical trials are exploring combined audible-infrasonic therapies for tinnitus, where low-frequency components (below 20 Hz) are integrated with higher tones to desensitize auditory pathways, showing preliminary reductions in perceived severity without exceeding safe exposure parameters.^[107] These protocols emphasize individualized dosing and monitoring to balance therapeutic benefits with minimal risk.^[108]

Cultural and Societal Aspects

Representations in Media

Infrasound has been employed in film sound design to evoke subtle unease and atmospheric tension, particularly in horror genres where low-frequency tones below 20 Hz are used to induce physiological responses without conscious auditory perception. Research shows such sounds can trigger anxiety and chills by vibrating the eyeballs and inner ear.^[85] Similarly, sci-fi films like Denis Villeneuve's Arrival (2016) utilize subtle low-frequency throbs in the sound mix to underscore alien communication, blending low-frequency rumbles with the heptapods' vocalizations for an otherworldly immersion that emphasizes non-linear time perception.^[109] In music and sound art, experimental composers have integrated infrasound to expand sensory experiences and challenge conventional listening. Pauline Oliveros, a pioneer in deep listening practices, explored ultra-low frequencies in her improvisational works, such as those using electronic tape manipulation to incorporate sub-20 Hz vibrations, fostering immersive environments that blur hearing and feeling.^[110] Other artists, like Sarah Angliss in her 2003 "Infrasonic" project, composed "soundless music" with 17-19 Hz tones to provoke emotional responses, including sorrow and fear, during live performances monitored for physiological effects.^[111] Documentaries have portrayed infrasound's natural roles more accurately, focusing on scientific applications rather than sensationalism. The BBC Earth's Animal Super Senses series (2015) featured a segment on elephant infrasound communication, demonstrating how African elephants produce rumbles below 20 Hz to detect distant storms and coordinate over kilometers, using seismic and acoustic recordings to illustrate long-range propagation.^[112] Popular science media, including the Comprehensive Nuclear-Test-Ban Treaty Organization's (CTBTO) Sniffing for Nuclear Explosions (2015), explained infrasound networks for global monitoring, showing how microbarometers detect low-frequency waves from nuclear tests or volcanoes, traveling thousands of kilometers with minimal attenuation.^[113] Depictions in media often exaggerate infrasound's effects for dramatic impact, overemphasizing spontaneous fear induction while omitting the need for high intensities (typically above 100 dB) to elicit responses, as low-level exposure produces negligible physiological changes in controlled studies.^[114] This inaccuracy stems from early experiments like the 2003 Infrasonic concert, inspired by Vic Tandy's research, where 19 Hz tones at moderate volumes caused unease in participants, but real-world media applications rarely contextualize dosage or duration, leading to misconceptions about infrasound's omnipotent dread.^[115] Such portrayals draw briefly from documented psychological effects, like mild disorientation, but prioritize narrative tension over scientific precision.^[116]

Associations with Anomalies

Infrasound has been linked to reports of anomalous phenomena, such as ghost sightings and UFO encounters, where low-frequency vibrations induce physiological responses that mimic supernatural experiences. These associations stem from scientific investigations demonstrating how infrasound can cause unease, visual distortions, and auditory illusions without any paranormal involvement. Pioneering studies in the late 1990s and early 2000s highlighted infrasound's role in "haunted" sensations. In 1998, engineer Vic Tandy and psychologist Tony Lawrence examined recurring reports of a gray apparition and oppressive atmosphere in Tandy's laboratory at Coventry University. They identified a 19 Hz standing wave produced by a nearby fan, which resonated with the human eyeball at its natural frequency of approximately 18-19 Hz, causing blurred peripheral vision and the illusion of a ghostly figure; the low frequency also triggered feelings of dread and anxiety through vestibular and autonomic nervous system effects.^[84] Building on this, acoustic scientist Richard Lord, in collaboration with psychologist Richard Wiseman, conducted experiments from 1998 to 2003 at allegedly haunted sites like Mary King's Close in Edinburgh. Their work confirmed elevated 19 Hz infrasound levels from environmental sources, such as wind through underground tunnels, correlating with participants reporting chills, sensations of being watched, and emotional discomfort, replicating "haunted" feelings in controlled settings.^[117] Similar mechanisms have been proposed for UFO and other mystery events involving unexplained hums and vibrations. In the 1980 Rendlesham Forest incident near RAF Woodbridge, UK, witnesses described unidentified lights in the woods. Meteor airbursts provide another example, as seen in the 1908 Tunguska event in Siberia, where the explosion produced powerful infrasound waves detectable thousands of kilometers away, creating anomalous booms, ground tremors, and atmospheric glows that eyewitnesses later interpreted as extraordinary or extraterrestrial phenomena.^[118] Despite these links, rigorous scientific analysis reveals no evidence supporting paranormal causation for such anomalies, emphasizing instead verifiable physiological and environmental explanations. Infrasound's subtle effects on the inner ear and brain can amplify suggestibility, leading to misattributions of natural stimuli. Research has connected infrasound exposure to sensations of "presences" and hallucinatory experiences, such as those during sleep paralysis episodes involving immobilizing fear due to disrupted REM sleep combined with vibrational unease.^[119] Media portrayals have often sensationalized these associations, fostering pseudoscientific narratives that portray infrasound as a gateway to the supernatural, while downplaying empirical findings from acoustics and psychology that favor mundane origins like industrial vibrations or atmospheric conditions.^[114]

References

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NASA Microphone Detects Turbulence Hundreds of Miles Away
Mar 16, 2021 · Infrasound consists of pitches too low to be heard by the human ear, between 0.001 and 20 hertz. infrasound microphone. Researchers at NASA's ...
[2]
infrasonicasket exploring the musical possibilities of infrasound
Infrasound is defined as the range of frequencies below the range of human hearing: 20 Hz down to .001 Hz. It is a relatively unexplored range of sounds that ...
[3]
Infrasound transmission in the human ear: Implications for acoustic ...
It is widely believed that human hearing is insensitive to infrasound, defined as frequencies below 20 Hz. However, there is evidence that infrasound can alter ...
[4]
[PDF] Chapter 4 Findings Based on the detailed review of the scientific ...
3. Infrasound refers to vibrations with frequencies below 20 Hz. Infrasound at amplitudes over 100-110 dB can be heard and felt.<|control11|><|separator|>
[5]
Volcano Watch — Infrasound is coming to HVO…can you hear it?
Infrasound monitoring was developed for detecting nuclear explosions. Nuclear explosions produce infrasound that can propagate large distances and, thus, can be ...
[6]
Infrasound | GTRI - Georgia Institute of Technology
Dec 15, 2021 · Infrasound is a low-frequency sound, below 20 Hertz, that cannot be heard by humans, produced by sources like tornados and earthquakes.
[7]
High-Flying Recording Studio Captures Deep Bass Infrasound ...
Infrasound sources include volcanoes, earthquakes, ocean waves, the aurora, explosions, rocket launches…and many more. The power of infrasound lies in its ...
[8]
Understanding Sound - Natural Sounds (U.S. National Park Service)
Jul 3, 2018 · At the other end of the spectrum are very low-frequency sounds (below 20 Hz), known as infrasound. Elephants use infrasound for communication, ...Missing: properties | Show results with:properties
[9]
Negative Effect of High-Level Infrasound on Human Myocardial ...
Exposure to high levels of infrasound (more than 100 dBz) interferes with cardiac muscle contractile ability, as early as one hour after exposure.
[10]
[PDF] Acoustics Today - Consortium for Verification Technology
Because the absorption of sound in the atmosphere decreases with fre- quency, the low-frequency infrasound band holds the promise of signal detec- tion over ...
[11]
Tree-cover and topography effects on local-infrasound propagation
Infrasound can propagate very long distances and remain at measurable levels. As a result infrasound sensing is used for remote monitoring in many applications.
[12]
The correction of infrasound signals for upper atmospheric winds
Infrasound waves propagate in the atmosphere by a well known mechanism produced by refraction of the waves, return to earth, and reflection at the surface ...
[13]
[PDF] SIR 2024–5062 Chap. C: Infrasound for Volcano Monitoring
Aug 16, 2013 · As with most monitoring data, infrasound provides the most useful information when combined with other geophysical and remote sensing data.
[14]
[PDF] Infrasound produced by a small pile fire - USDA Forest Service
Jan 28, 2025 · Infrasound is a widely used monitoring tool for hazardous processes occurring at Earth's surface and in the atmosphere, including volcanoes. [1] ...
[15]
Infrasound Sensor Technology | T2 Portal
An infrasound microphone enables remote detection of aircraft wake vortices, clear air turbulence, tornadoes, and seismic events.
[16]
[PDF] Measuring Infrasound from the Maritime Environment - CDIP
Currently, infrasound is measured using land-based sensors. Maritime measurement, using boats, buoys, or USVs, is being explored to enhance detection and ...
[17]
SHOULD LIMIT VALUES BE SET FOR INFRASOUND CAUSED BY ...
INTRODUCTION. From the physical point of view, infrasound is defined as an acoustic wave in the frequency range of 0.1–20 Hz [1], while the international ...Missing: properties | Show results with:properties
[18]
The Role of Infrasound and Audible Acoustic Sound in Modulating ...
Apr 27, 2025 · Infrasound enhances bone growth, 100 Hz sound promotes fibroblast migration, and 10-20 kHz frequencies stimulate epidermal wound healing.
[19]
Elephant Sound – K. Lisa Yang Center for Conservation Bioacoustics
Infrasound is sound that is below the threshold of human hearing. The figure to the right shows the frequency (or tone) for average humans when they talk, ...Missing: definition properties
[20]
Infrasound monitoring - CTBTO
These waves are below the frequency band audible to the human ear, which typically ranges from 20 to 20,000 Hertz.
[21]
Exploring Infrasound: Importance, Applications And How To Measure It
Apr 15, 2024 · Infrasound refers to sound waves with frequencies below the lower limit of human audibility, typically below 20 Hz and down to 0.001 Hz.
[22]
What is infrasound? - ScienceDirect.com
Infrasound is sound below 20 Hz, or acoustic oscillations below the low frequency limit of audible sound (about 16 Hz), and is often considered as a ...
[23]
[PDF] Infrasound and its impact on people - National Wind Watch
Infrasound refers to extreme bass waves or vibrations whose frequency is below the hearing range of the human ear (from 20 Hz to 22 kHz). Infrasound is elastic ...
[24]
Infrasound, sound waves that nothing can stop | CNRS News
Oct 18, 2024 · Infrasound waves, very low-frequency acoustic waves below 20 hertz (Hz) that can propagate over great distances.Missing: definition | Show results with:definition
[25]
Sound Pressure Level - The Engineering ToolBox
The lowest sound pressure possible to hear is approximately 2×10-5 Pa (20 micro Pascal, 0.02 mPa) or 2 ten billionths of an atmosphere. This minimum audible ...Missing: infrasound | Show results with:infrasound
[26]
Sound Pressure Level (SPL) | Svantek Academy
Using the formula Lp=10lg (p/p0)2, where p is the sound pressure in pascals, and p0 is the reference sound pressure of 20 μPa.Missing: infrasound | Show results with:infrasound
[27]
Infrasonic Sound - HyperPhysics
The term "infrasonic" applied to sound refers to sound waves below the frequencies of audible sound, and nominally includes anything under 20 Hz.
[28]
[PDF] Measurement and characterization of infrasound from a tornado ...
Sep 3, 2019 · Tornadoes generally produce infrasound between. 0.5 Hz (k % 686 m) and 10 Hz (k % 34.3 m), where k is the acoustic wavelength. Bedard (1998) ...<|separator|>
[29]
[PDF] Physics of Infrasound Propagation
Mar 29, 2022 · Attenuation is small ∼ (frequency)2. • Sources are large or catastrophic. Working definition: 0.05 Hz to 20 Hz. • between buoyancy waves and ...
[30]
Global morphology of infrasound propagation - NASA ADS
Atmospheric sound waves in the 0.02-10 Hz region, also known as infrasound, exhibit long-range global propagation ... attenuation (∼0.01 dB km -1 at 0.1 hz), ...
[31]
Influence of atmospheric structure and topography on infrasonic ...
Feb 27, 2014 · The absorption of infrasonic waves by wave dissipation, which is described by the attenuation coefficient (in dB/km), is proportional to the ...
[32]
Characterization of infrasound from lightning - Assink - AGU Journals
Aug 2, 2008 · [26] Attenuation is the dissipation of wave energy because of geometrical spreading and the absorbing properties of the atmosphere. ... density ...2. Methods · 3. Observations · 4. Attenuation
[33]
(PDF) Transmission of infrasound through gas-solid interfaces
Jul 15, 2020 · In this paper, we study the effects of shear rigidity on sound transmission through an interface with a large mass density contrast. It is found ...
[34]
Long-range atmospheric infrasound propagation from subsurface ...
Feb 25, 2020 · Low-frequency acoustic waves, i.e., infrasound, propagate in the atmosphere in a frequency range between 0.01 to 20 Hz. Infrasonic waves in the ...
[35]
Infrasound from Earthquakes - ResearchGate
Aug 10, 2025 · Infrasound observations allow that conclusions about the characteristics of the generating earthquake can be drawn. Mutschlecner and Whitaker ( ...<|control11|><|separator|>
[36]
Abnormal infrasound signals before 92 M ≧ 7.0 worldwide ...
Jun 5, 2011 · The maximum amplitude of the abnormal infrasound signal generally exceeds 8 Pa in sound pressure. The statistical analyses further indicate that ...
[37]
The Characteristics of Infrasound, its Propagation and Some Early ...
Low frequency acoustic signals were first discovered after the eruption of the Krakatoa (Indonesia) in 1883. Owing to its low frequency content, this infrasound ...
[38]
Locating cannons by sound ranging in World War I - ResearchGate
Aug 9, 2025 · Acoustic and seismic ranging methods have been used from as early as World War I for locating artillery positions and were fundamental to the ...<|control11|><|separator|>
[39]
Balloon detects first signs of a 'sound tunnel' in the sky | Science
Apr 27, 2022 · After geophysicist Maurice Ewing discovered the SOFAR channel in 1944, he set out to find an analogous layer in the sky. At an altitude of ...Missing: studies | Show results with:studies
[40]
Infrasonic Symphony - Science News
Jan 3, 2004 · Infrasonic research gained significant attention and funding in the 1950s, when the United States and the Soviet Union used infrasound to detect ...<|control11|><|separator|>
[41]
Atmospheric Infrasound - American Institute of Physics
Among the technologies explored during those early years of the Cold War were seismic arrays, electro- magnetic (radio to gamma-ray) sensors, and arrays of.
[42]
Passive infrasound monitoring is an active area of study
Aug 1, 2018 · Infrasound research has been driven largely by defense needs, namely to monitor nuclear and chemical explosions. Investment in the method slowed ...
[43]
Observing Systems by Technology - Physical Sciences Laboratory
Infrasonic and near-infrasonic signatures may provide advanced warning and monitoring of these extreme events. Infrasonic sensors invented at PSD are the basis ...
[44]
[PDF] Infrasound and the Infrasonic Monitoring of Atmospheric Nuclear ...
Dec 27, 2024 · This report reviews past work in infrasound and atmospheric acoustics for monitoring CTBT compliance, covering measurement, sources, and ...
[45]
The International Monitoring System | CTBTO
Building an IMS station involves four steps: site surveys, installation, certification and operation. Firstly, a site survey is conducted to assess suitability ...
[46]
Improved infrasound array processing with robust estimators
Mar 9, 2020 · Here we examine the effectiveness of robust regression estimators (L 1 -norm regression, M-estimators and least trimmed squares) for infrasound array ...
[47]
Narrow‐Band Least‐Squares Infrasound Array Processing
Jun 10, 2022 · Infrasound data from arrays can be used to detect, locate, and quantify a variety of natural and anthropogenic sources from local to remote ...Missing: post- | Show results with:post-
[48]
Seismoacoustic monitoring of eastern mediterranean earthquakes ...
Oct 25, 2025 · Similar to earthquake early warning systems, infrasound monitoring can be used to provide prompt alerts of flash floods resulting from ...
[49]
[PDF] Infrasound Signals Detected of Auroral Electrojet Arcs in 2020 by ...
Sep 12, 2025 · The auroral electrojet arcs display generate low frequency acoustic signals in the process which are sensitive to the sensors of the infrasound ...Missing: correlations climate
[50]
On the Possible Infrasound Generation by Sprites - Sage Journals
Sentman D. D., Wescott E. M., Osborne D. L., Hampton D. L. and Heavner M. J., Preliminary results from the sprites 94 aircraft Campaign:! Red sprites, Geophys.Missing: Jim | Show results with:Jim
[51]
Infrasound signals of fireballs detected by the Geostationary ...
This paper aims to study and compare fireball data from the Geostationary Lightning Mappers (GLMs) on board the two Geostationary Observational Environmental ...
[52]
Infrasound for volcano monitoring - USGS.gov
Oct 4, 2024 · However, wind and ocean noise also produce infrasound, and spatiotemporal variability in the atmosphere can affect the propagation of infrasound ...Missing: events | Show results with:events
[53]
Research - Robin Matoza
In addition to volcanoes, sources of infrasound include earthquakes, mass-wasting events, bolides, ocean wave-wave interactions, lightning, hurricanes ...
[54]
[PDF] Infrasound from Tornados: Theory, Measurement, and Prospects for ...
Introduction. Infrasound is propagating sound waves with frequencies below the range of human hearing. A practical frequency range for infrasound that will ...
[55]
The radiation of atmospheric microbaroms by ocean waves
Aug 6, 2025 · A two-fluid model, air over seawater, is used to investigate the radiation of infrasound by ocean waves. The acoustic radiation which ...
[56]
Natural and Anthropogenic Sources of Seismic, Hydroacoustic, and ...
Natural sources of seismic, hydroacoustic, and infrasonic waves include earthquakes, microseisms, and microbaroms. Anthropogenic sources include drop weights ...<|separator|>
[57]
Researchers Use Whale Calls to Probe Undersea Geology
Feb 16, 2021 · The study finds that fin whale songs are powerful enough to reverberate through the Earth's crust, allowing scientists to study its thickness and structure.
[58]
Visualizing Sound Emission of Elephant Vocalizations: Evidence for ...
Nov 14, 2012 · Our results showed that the female elephants in our analysis produced two distinct types of rumble vocalizations based on vocal path differences.
[59]
Low frequency and infrasonic vocalizations from tigers - Acoustics.org
In 2000 it was discovered that tigers, like whales, elephants, rhinos, and other animals, could create sounds low in frequency and some that are infrasonic.
[60]
The infrasonic signature of three exceptional rocket launches
Apr 2, 2024 · Infrasound from rocket launches, including lift-off, flight and sonic boom signals, can be detected at infrasound arrays hundreds to thousands of kilometers ...
[61]
1001 Rocket Launches for Space Missions and Their Infrasonic ...
Apr 6, 2021 · Infrasound array processing is applied to monitor and characterize atmospheric explosions in the context of the Comprehensive ...
[62]
Wind turbine infrasound: Phenomenology and effect on people
Wind turbine infrasound produces perceptible vibrations and audible sound in nearby buildings. Most people are unaffected by wind turbine infrasound.
[63]
Potential Effects on Human Safety and Health from Infrasound and ...
A variety of machines and installations in industry transmit infrasound noise directly (for instance, cleaning baths, several productive machines, cutting ...1. Introduction · 2. Materials And... · 4. Measurements And Results<|separator|>
[64]
Prediction of regional infrasound produced by supersonic sources ...
Mar 1, 2024 · Anthropogenic supersonic objects such as rockets and aircraft produce observable infrasonic signals that can similarly be utilized in remote ...
[65]
Infrasonic Signals from Large Mining Explosions - GeoScienceWorld
Apr 1, 2008 · We study infrasonic signals from large surface mining explosions in Wyoming. Detections at the Pinedale Infrasound Array (PDIAR) (obtained using ...Missing: infrasound | Show results with:infrasound
[66]
[PDF] Atmospheric Infrasound - atmo.arizona.edu
Natural Infrasound-Potential Applications and Future Research. Sources. Avalanches. Meteors. Ocean waves. Severe-weather systems. Tornadoes. Turbulence.
[67]
[PDF] Infrasound: Connecting the Solid Earth, Oceans, and Atmosphere
Feb 9, 2012 · Infrasonic propagation is controlled by a variety of phenomena: advection through a windy atmo- sphere, refraction due to sound speed gradients, ...
[68]
Characteristics, relationships and precision of direct acoustic-to ...
In agreement with modelling, we find that the ground motions induced by acoustic-to-seismic coupling attenuate rapidly with depth. We confirm the modelled ...
[69]
https://l2a.ucsd.edu/pub/hedlin_2012a.pdf
[70]
[PDF] prediction of tornado infrasound within the turbulent atmosphere
Infrasound propagation is altered by atmospheric turbulence, which must be accounted for to detect tornadoes.
[71]
[PDF] Infrasound from Convective Storms, Part II: A Critique of Source ...
I critically examine several acoustic radiation mechanisms that have been suggested to explain the ultra-low-frequency.<|control11|><|separator|>
[72]
Diving Deeper Into the Sound of Blue Whales | Brüel & Kjær - HBK
Blue whales communicate via low frequencies (for a 15 Hz signal the wavelength is around 100 m) so a special method was also needed to locate exactly where the ...<|control11|><|separator|>
[73]
Infrasound and the Avian Navigational Map
Apr 1, 2000 · Laboratory experiments show that pigeons have extraordinary low-frequency hearing and can detect sounds as low as 0.05 Hz (Kreithen and ...Missing: 0.5-10 | Show results with:0.5-10
[74]
Co-occurrence of beaked whale strandings and naval sonar in the ...
Feb 19, 2020 · Mid-frequency active sonar (MFAS), used for antisubmarine warfare (ASW), has been associated with multiple beaked whale (BW) mass stranding events.
[75]
Chronic Exposure to Low Frequency Noise at Moderate Levels ...
Chronic exposure to environmental infrasound has been shown to affect blood pressure, resulting in hypertension in humans [7]. Furthermore, exposure to moderate ...
[76]
https://journals.biologists.com/jeb/article/203/7/1103/8430/Infrasound-and-the-Avian-Navigational-Map
[77]
Secret Sounds of Elephants - National Wildlife Federation
Apr 1, 2005 · Both trunk and feet contain two kinds of pressure-sensitive nerve endings—one that detects infrasonic vibrations and another that responds to ...
[78]
[PDF] N76-26818 - NASA Technical Reports Server
Vestibular system. Subjective reports of dis- orientation, vertigo, nausea, and interference with postural equilibrium during high-intensity noise exposure.<|separator|>
[79]
Review of Audiovestibular Symptoms Following Exposure to ...
Technology emitting infrasound such as wind turbines and rocket engines have produced isolated reports of vestibular symptoms, including dizziness and nausea ...
[80]
Effects of low-frequency noise from wind turbines on heart rate ...
Sep 8, 2021 · Exposure to LFN from wind turbines results in headaches, difficulty concentrating, irritability, fatigue, dizziness, tinnitus, aural pain sleep ...
[81]
(PDF) A Ghost in the Machine - ResearchGate
Aug 6, 2025 · We show how a 19hz standing air wave may under certain conditions create sensory phenomena suggestive of a ghost.Missing: psychological | Show results with:psychological
[82]
The fear frequency | Science - The Guardian
Oct 15, 2003 · Tandy learned that low frequencies in this region can affect humans and animals in several ways, causing discomfort, dizziness, blurred vision ( ...
[83]
The Infrasonic 17 Hz Tone Experiment Induced Revulsion And Fear ...
Dec 6, 2024 · In 2003, scientists subjected 750 volunteers to a strange experiment, in the form of a fear and anxiety-inducing concert.
[84]
Is there really a noise that makes you poop yourself?
Oct 5, 2021 · However, scientists have tested the effects of different sound frequencies on the human body and found no evidence for the infamous brown note.Missing: infrasound debunked
[85]
Directive 2003/10/EC - noise | Safety and health at work EU-OSHA
Nov 14, 2024 · The exposure limit values fixed at 87 decibels shall take into account of the attenuation provided by personal protective equipment (hearing ...Missing: infrasound | Show results with:infrasound
[86]
September 2017 DPRK Nuclear Test - CTBTO
Since 3 September 2017, the IMS network has detected more than 30 smaller aftershocks in the vicinity of the test site. Mounting evidence suggests that the ...
[87]
A multi-technology analysis of the 2017 North Korean nuclear test - SE
Jan 15, 2019 · The 2017 North Korean test had a yield of hundreds of kT TNT, with a 400 kT estimate. Seismic data showed a 0.6 km depth, and satellite data ...
[88]
Atmospheric waves and global seismoacoustic observations of the ...
May 12, 2022 · The Hunga Tonga undersea volcanic eruption was one of the most powerful recorded, with audible sound detected more than 10,000 kilometers ...
[89]
Study on the characteristic mechanisms of infrasonic precursors ...
The amplitude or energy of an infrasound anomalous signal is related to the magnitude of the corresponding earthquake.
[90]
Developing the world's first tsunami sensor that connects infrasound ...
One result of these efforts are infrasound tsunami sensors that detect the occurrence of tsunamis and provide preliminary reports on their size and arrival time ...
[91]
Establishing the fundamentals for an elephant early warning and ...
Sep 4, 2015 · Elephants make extensive use of powerful infrasonic calls (rumbles) that travel distances of up to several kilometers. This makes elephants well ...
[92]
Analysis of infrasound array data from tornadic storms in the ...
Sep 20, 2024 · The analyses reveal that on the systems deployed, the dominant band of coherent infrasound measured from the tornadic storms was between 2 and 6 ...II. INFRASOUND SENSOR... · III. SUMMARY OF... · VI. NON-TORNADIC STORM...
[93]
Space junk falling to Earth needs to be tracked: Meteoroid sounds ...
May 4, 2025 · Researchers are using infrasound sensors to track these objects, including bolides, which are meteoroids breaking apart in the sky. New research ...
[94]
Identification of Quarry Blasts Aided by Infrasound Data
May 6, 2021 · We introduce an automatic search method to associate infrasound detections with a preliminary list of explosions detected by the seismic network.
[95]
[PDF] additional infrasonic studies of earthquakes and mining blasts ...
The goal of this research is to be able to distinguish between earthquakes and small mining blasts using discriminants established using either infrasound or in ...
[96]
Detecting Large Explosions using Infrasound Data Augmentation ...
Large explosions are detected using infrasound waves, machine learning, and a physics-based data augmentation method to create synthetic training data.
[97]
In-ear infrasonic hemodynography with a digital health device ... - NIH
Dec 22, 2022 · In-ear infrasonic hemodynography (IH) can measure low-frequency vibrations (<20 Hz) created by vital organs as an acoustic waveform.
[98]
New Ultrasound Technology Potentially Revolutionizes Respiratory ...
Mar 19, 2024 · Doctors can identify potential disease-related abnormalities in the respiratory system by evaluating sound vibrations produced by the ...<|separator|>
[99]
Sonic vibration ameliorates inflammatory diseases via the up ...
Sonic vibration (SV), or vibroacoustic therapy, is applied to enhance local and systemic blood circulation and alleviate pain using low-frequency sine wave ...Missing: infrasound physiotherapy
[100]
https://ui.adsabs.harvard.edu/abs/2021AGUFM.V24A..04W/abstract
[101]
A longitudinal, randomized experimental pilot study to investigate ...
Feb 4, 2021 · Specifically engineered infrasonic (6 Hz, 80–90 dB) vs. sham devices were installed in participants' (N = 38) bedrooms and active for 28 nights.
[102]
[PDF] The Neural Basis of Groove Sensations - arXiv
The human vestibular system is particularly sensitive to low-frequency vibrations and infrasound, with the otolithic organs playing a key role in modulating ...<|separator|>
[103]
Possible Mechanisms for the Effects of Sound Vibration on Human ...
May 18, 2021 · It begins by narrowing music to sound and sound to vibration. The focus is on low frequency sound (up to 250 Hz) including infrasound (1–16 Hz).
[104]
[PDF] HEALTH RISKS DUE TO EXPOSURE OF LOW-FREQUENCY NOISE
Oct 12, 2009 · It seems, on the basis of existing data, that the threshold for infrasonic effects is approximately 120 dB SPL. It is further concluded that ...
[105]
Chronic tinnitus is quietened by sound therapy using a novel cross ...
We introduce a novel modulation of broadband sounds which eliminates correlations between all frequency pairs close to the tinnitus frequency.
[106]
Medical and non-medical protection standards for ultrasound and ...
A limit on sound pressure level of 100 dB for the general population is recommended. The absence of protection standards for infrasound relates to difficulties ...
[107]
Directors Close-Up Recap: 'Arrival' Filmmakers Denis Villeneuve ...
Feb 23, 2017 · ... low frequency sonic throb which utterly dominates the sound mix at several critical points in the film. “We incorporated sound design well ...<|separator|>
[108]
(PDF) Infrasonic Music - ResearchGate
Aug 7, 2025 · Low-frequency sound on the cusp of the audible offers the possibility of redefining the way we think about listening to music.
[109]
Infrasonic – haunted music? - Sarah Angliss
Infrasonic (aka Soundless Music) was a controlled psychological experiment, in the form of two back-to-back concerts. These concerts were highly unusual.Missing: 19th century
[110]
Mystery of Elephant Infrasounds Revealed | Animal Super Senses
Nov 27, 2015 · Patrick finds out the fascinating way in which elephants use infrasound to detent impending storms. Subscribe to BBC Earth: ...Missing: resonance | Show results with:resonance
[111]
'Sniffing' for Nuclear Explosions - YouTube
Jul 10, 2015 · The Comprehensive Nuclear-Test-Ban Treaty Organization has developed a network of sensors that feel, hear and sniff the planet for signs of ...
[112]
Silent sounds hit emotional chords | Science - The Guardian
Sep 8, 2003 · Scientists have found a way to add a spine-tingling dimension to modern music. They played an experimental organ pipe too low to be heard and then collected ...Missing: 19th | Show results with:19th
[113]
Annoyance, perception, and physiological effects of wind turbine ...
Apr 2, 2021 · These findings suggest that the levels of infrasound in the current study did not affect perception and annoyance or autonomic nervous system responses.
[114]
[PDF] Something in the Cellar - Richard Wiseman
The cellar was a prime opportunity to test the theory that infrasound could cause humans to experience hallucinations suggestive of an apparition. Located next ...Missing: psychological | Show results with:psychological
[115]
The Rendlesham Incident - Some Lessons for UFOlogy - The Skeptic
Apr 7, 2006 · When the events in Rendlesham Forest happened I was still in my 20s and relatively inexperienced. ... humming noises, strange electrical ...
[116]
Blast from the past: Solving the Tunguska mystery | New Scientist
Jun 26, 2013 · Remember, this was the era of the first reported UFO sightings. Many ... The explosion also produced infrasound waves, inaudible to ...
[117]
The science behind seeing ghosts - BBC Three
Aug 15, 2023 · To investigate these two theories, Chris and his team created an artificial haunted room, exposing participants to infrasound and ...Missing: pseudoscience media