Infrasound
Encyclopedia
Infrasound is sound that is lower in frequency than 20 Hz (Hertz
) or cycles per second, the "normal" limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure
must be sufficiently high. The ear
is the primary organ for sensing infrasound, but at higher levels it is possible to feel infrasound vibrations in various parts of the body.
The study of such sound waves is sometimes referred to as infrasonics, covering sounds beneath 20 Hz down to 0.001 Hz. This frequency range is utilized for monitoring earthquake
s, charting rock and petroleum formations below the earth, and also in ballistocardiography
and seismocardiography to study the mechanics of the heart. Infrasound is characterized by an ability to cover long distances and get around obstacles with little dissipation
.
to locate artillery
. One of the pioneers in infrasonic research was French scientist Vladimir Gavreau
, born in Russia as Vladimir Gavronsky. His interest in infrasonic waves first came about in his lab during the 1960s, when he and his lab assistants experienced pain in the ear drums and shaking lab equipment, but no audible sound was picked up on his microphones. He concluded it was infrasound caused by a large fan and duct system and soon got to work preparing tests in the labs. One of his experiments was an infrasonic whistle, an oversized organ pipe
.
, surf
, lee waves, avalanche
s, earthquake
s, volcano
es, bolides, waterfall
s, calving
of iceberg
s, aurorae
, lightning
and upper-atmospheric lightning
.
Nonlinear ocean wave
interactions in ocean storms produce pervasive infrasound vibrations around 0.2 Hz, known as microbarom
s.
Infrasound can also be generated by man-made processes such as sonic boom
s and explosion
s (both chemical and nuclear
), by machinery such as diesel engine
s and older designs of down tower wind turbine
s and by specially designed mechanical transducers (industrial vibration tables) and large-scale subwoofer
loudspeakers such as rotary woofer
s. The Comprehensive Nuclear-Test-Ban Treaty Organization Preparatory Commission
uses infrasound as one of its monitoring technologies (along with seismic
, hydroacoustic
, and atmospheric radionuclide
monitoring).
Whale
s, elephant
s, hippopotamus
es, rhinoceros
, giraffe
s, okapi
, and alligator
s are known to use infrasound to communicate over distances—up to hundreds of miles in the case of whales. It has also been suggested that migrating bird
s use naturally generated infrasound, from sources such as turbulent airflow over mountain
ranges, as a navigation
al aid. Elephants, in particular, produce infrasound waves that travel through solid ground and are sensed by other herds using their feet, although they may be separated by hundreds of kilometres.
Infrasound may also be used for long-distance communication in African elephants. These calls range from 15–35 Hz and can be as loud as 117 dB
, allowing communication for many kilometres, with a possible maximum range of around 10 km (6 mi). These calls may be used to coordinate the movement of herds and allow male elephants to find mates.
The dynamic range of the auditory system decreases with decreasing frequency. This compression can be seen in the equal-loudness-level contours, and it implies that a slight increase in level can change the perceived loudness from barely audible to loud. Combined with the natural spread in thresholds
within a population, it may have the effect that a very low frequency sound which is inaudible to some people may be loud to others.
Infrasound has been known to cause feelings of awe or fear in humans. Since it is not consciously perceived, it can make people feel vaguely that supernatural
events are taking place.
The infrasound and low-frequency noise produced by some wind turbine
s is believed by some to cause "wind-turbine syndrome" (headaches, dizziness, nausea) in humans and other animals close to the turbines, although there are "mixed opinions on whether wind turbines emit infrasound and if the amount is any more than that emitted by diesel engines or waves crashing on the beach."
over the course of two performances, each consisting of four musical pieces. Two of the pieces in each concert had 17 Hz tones played underneath. In the second concert, the pieces that were to carry a 17 Hz undertone were swapped so that test results would not focus on any specific musical piece. The participants were not told which pieces included the low-level 17 Hz near-infrasonic tone. The presence of the tone resulted in a significant number (22%) of respondents reporting anxiety, uneasiness, extreme sorrow, nervous feelings of revulsion or fear, chills down the spine and feelings of pressure on the chest. In presenting the evidence to British Association for the Advancement of Science
, Professor Richard Wiseman
said, "These results suggest that low frequency sound can cause people to have unusual experiences even though they cannot consciously detect infrasound. Some scientists have suggested that this level of sound may be present at some allegedly haunted sites and so cause people to have odd sensations
that they attribute to a ghost
—our findings support these ideas."
, a lecturer at Coventry University
, suggested that an infrasonic signal of 19 Hz might be responsible for some ghost sightings
. Tandy was working late one night alone in a supposedly haunted laboratory at Warwick
, when he felt very anxious and could detect a grey blob out of the corner of his eye. When Tandy turned to face the grey blob, there was nothing.
The following day, Tandy was working on his fencing
foil
, with the handle held in a vise
. Although there was nothing touching it, the blade started to vibrate wildly. Further investigation led Tandy to discover that the extractor fan in the lab was emitting a frequency of 18.98 Hz, very close to the resonant frequency of the eye given as 18 Hz by NASA. This was why Tandy had seen a ghostly figure—it was an optical illusion caused by his eyeballs resonating. The room was exactly half a wavelength in length, and the desk was in the centre, thus causing a standing wave
which caused the vibration of the foil.
Tandy investigated this phenomenon further and wrote a paper entitled The Ghost in the Machine. Tandy carried out a number of investigations at various sites believed to be haunted, including the basement of the Tourist Information Bureau next to Coventry Cathedral
and Edinburgh Castle
.
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
) or cycles per second, the "normal" limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure
Sound pressure
Sound pressure or acoustic pressure is the local pressure deviation from the ambient atmospheric pressure caused by a sound wave. Sound pressure can be measured using a microphone in air and a hydrophone in water...
must be sufficiently high. The ear
Ear
The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....
is the primary organ for sensing infrasound, but at higher levels it is possible to feel infrasound vibrations in various parts of the body.
The study of such sound waves is sometimes referred to as infrasonics, covering sounds beneath 20 Hz down to 0.001 Hz. This frequency range is utilized for monitoring earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s, charting rock and petroleum formations below the earth, and also in ballistocardiography
Ballistocardiography
The ballistocardiograph is a measure of ballistic forces on the heart. Ballistocardiography is a technique for producing a graphical representation of repetitive motions of the human body arising from the sudden ejection of blood into the great vessels with each heart beat...
and seismocardiography to study the mechanics of the heart. Infrasound is characterized by an ability to cover long distances and get around obstacles with little dissipation
Dissipation
In physics, dissipation embodies the concept of a dynamical system where important mechanical models, such as waves or oscillations, lose energy over time, typically from friction or turbulence. The lost energy converts into heat, which raises the temperature of the system. Such systems are called...
.
History and study
Infrasound was used by the allies of World War IWorld War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
to locate artillery
Artillery
Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...
. One of the pioneers in infrasonic research was French scientist Vladimir Gavreau
Vladimir Gavreau
Vladimir Gavreau was a French scientist making experiments on the biological effects of infrasound....
, born in Russia as Vladimir Gavronsky. His interest in infrasonic waves first came about in his lab during the 1960s, when he and his lab assistants experienced pain in the ear drums and shaking lab equipment, but no audible sound was picked up on his microphones. He concluded it was infrasound caused by a large fan and duct system and soon got to work preparing tests in the labs. One of his experiments was an infrasonic whistle, an oversized organ pipe
Organ pipe
An organ pipe is a sound-producing element of the pipe organ that resonates at a specific pitch when pressurized air is driven through it. Each pipe is tuned to a specific note of the musical scale...
.
Sources
Infrasound sometimes results naturally from severe weatherSevere weather
Severe weather phenomena are weather conditions that are hazardous to human life and property.- Examples Include :Severe weather can occur under a variety of situations, but three characteristics are generally needed: a temperature or moisture boundary, moisture, and , instability in the...
, surf
Ocean surface wave
In fluid dynamics, wind waves or, more precisely, wind-generated waves are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They usually result from the wind blowing over a vast enough stretch of fluid surface. Waves in the...
, lee waves, avalanche
Avalanche
An avalanche is a sudden rapid flow of snow down a slope, occurring when either natural triggers or human activity causes a critical escalating transition from the slow equilibrium evolution of the snow pack. Typically occurring in mountainous terrain, an avalanche can mix air and water with the...
s, earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s, volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
es, bolides, waterfall
Waterfall
A waterfall is a place where flowing water rapidly drops in elevation as it flows over a steep region or a cliff.-Formation:Waterfalls are commonly formed when a river is young. At these times the channel is often narrow and deep. When the river courses over resistant bedrock, erosion happens...
s, calving
Ice calving
Ice calving, also known as glacier calving or iceberg calving, is a form of ice ablation or ice disruption. It is the sudden release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf, or crevasse...
of iceberg
Iceberg
An iceberg is a large piece of ice from freshwater that has broken off from a snow-formed glacier or ice shelf and is floating in open water. It may subsequently become frozen into pack ice...
s, aurorae
Aurora (astronomy)
An aurora is a natural light display in the sky particularly in the high latitude regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere...
, lightning
Lightning
Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
and upper-atmospheric lightning
Upper-atmospheric lightning
Upper-atmospheric lightning or upper-atmospheric discharge are terms sometimes used by researchers to refer to a family of short-lived electrical-breakdown phenomena that occur well above the altitudes of normal lightning and storm clouds. Upper-atmospheric lightning is believed to be electrically...
.
Nonlinear ocean wave
Ocean surface wave
In fluid dynamics, wind waves or, more precisely, wind-generated waves are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They usually result from the wind blowing over a vast enough stretch of fluid surface. Waves in the...
interactions in ocean storms produce pervasive infrasound vibrations around 0.2 Hz, known as microbarom
Microbarom
In acoustics, microbaroms, also known as the "voice of the sea",are a class of atmospheric infrasonic waves generated in marine stormsby a non-linear interaction of ocean surface waves with the atmosphere....
s.
Infrasound can also be generated by man-made processes such as sonic boom
Sonic boom
A sonic boom is the sound associated with the shock waves created by an object traveling through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding much like an explosion...
s and explosion
Explosion
An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave. If the shock wave is a supersonic detonation, then the source of the blast is called a "high explosive"...
s (both chemical and nuclear
Nuclear explosion
A nuclear explosion occurs as a result of the rapid release of energy from an intentionally high-speed nuclear reaction. The driving reaction may be nuclear fission, nuclear fusion or a multistage cascading combination of the two, though to date all fusion based weapons have used a fission device...
), by machinery such as diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
s and older designs of down tower wind turbine
Wind turbine
A wind turbine is a device that converts kinetic energy from the wind into mechanical energy. If the mechanical energy is used to produce electricity, the device may be called a wind generator or wind charger. If the mechanical energy is used to drive machinery, such as for grinding grain or...
s and by specially designed mechanical transducers (industrial vibration tables) and large-scale subwoofer
Subwoofer
A subwoofer is a woofer, or a complete loudspeaker, which is dedicated to the reproduction of low-pitched audio frequencies known as the "bass". The typical frequency range for a subwoofer is about 20–200 Hz for consumer products, below 100 Hz for professional live sound, and below...
loudspeakers such as rotary woofer
Rotary Woofer
The Rotary Woofer is a subwoofer-style loudspeaker which reproduces very low frequency content by using a conventional speaker voice coil's motion to change the pitch of a set of fan blades rotating at a constant speed...
s. The Comprehensive Nuclear-Test-Ban Treaty Organization Preparatory Commission
Comprehensive Test Ban Treaty
The Comprehensive Nuclear-Test-Ban Treaty bans all nuclear explosions in all environments, for military or civilian purposes. It was adopted by the United Nations General Assembly on 10 September 1996 but it has not entered into force.-Status:...
uses infrasound as one of its monitoring technologies (along with seismic
Seismology
Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic,...
, hydroacoustic
Hydrophone
A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change...
, and atmospheric radionuclide
Radionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
monitoring).
Whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
s, elephant
Elephant
Elephants are large land mammals in two extant genera of the family Elephantidae: Elephas and Loxodonta, with the third genus Mammuthus extinct...
s, hippopotamus
Hippopotamus
The hippopotamus , or hippo, from the ancient Greek for "river horse" , is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest...
es, rhinoceros
Rhinoceros
Rhinoceros , also known as rhino, is a group of five extant species of odd-toed ungulates in the family Rhinocerotidae. Two of these species are native to Africa and three to southern Asia....
, giraffe
Giraffe
The giraffe is an African even-toed ungulate mammal, the tallest of all extant land-living animal species, and the largest ruminant...
s, okapi
Okapi
The okapi , Okapia johnstoni, is a giraffid artiodactyl mammal native to the Ituri Rainforest, located in the northeast of the Democratic Republic of the Congo, in Central Africa...
, and alligator
Alligator
An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. There are two extant alligator species: the American alligator and the Chinese alligator ....
s are known to use infrasound to communicate over distances—up to hundreds of miles in the case of whales. It has also been suggested that migrating bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s use naturally generated infrasound, from sources such as turbulent airflow over mountain
Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...
ranges, as a navigation
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...
al aid. Elephants, in particular, produce infrasound waves that travel through solid ground and are sensed by other herds using their feet, although they may be separated by hundreds of kilometres.
Animal reactions to infrasound
Animals have been known to perceive the infrasonic waves going through the earth by natural disasters and can use these as an early warning. A recent example of this is the 2004 Indian Ocean earthquake and tsunami. Animals were reported to flee the area long before the actual tsunami hit the shores of Asia. It is not known for sure if this is the exact reason, as some have suggested that it was the influence of electromagnetic waves, and not of infrasonic waves, that prompted these animals to flee.Infrasound may also be used for long-distance communication in African elephants. These calls range from 15–35 Hz and can be as loud as 117 dB
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
, allowing communication for many kilometres, with a possible maximum range of around 10 km (6 mi). These calls may be used to coordinate the movement of herds and allow male elephants to find mates.
Human reactions to infrasound
Twenty Hz is considered the normal low frequency limit of human hearing. When pure sine waves are reproduced under ideal conditions and at very high volume, a human listener will be able to identify tones as low as 12 Hz. Below 10 Hz it is possible to perceive the single cycles of the sound, along with a sensation of pressure at the eardrums.The dynamic range of the auditory system decreases with decreasing frequency. This compression can be seen in the equal-loudness-level contours, and it implies that a slight increase in level can change the perceived loudness from barely audible to loud. Combined with the natural spread in thresholds
Absolute threshold of hearing
The absolute threshold of hearing is the minimum sound level of a pure tone that an average ear with normal hearing can hear with no other sound present. The absolute threshold relates to the sound that can just be heard by the organism...
within a population, it may have the effect that a very low frequency sound which is inaudible to some people may be loud to others.
Infrasound has been known to cause feelings of awe or fear in humans. Since it is not consciously perceived, it can make people feel vaguely that supernatural
Supernatural
The supernatural or is that which is not subject to the laws of nature, or more figuratively, that which is said to exist above and beyond nature...
events are taking place.
The infrasound and low-frequency noise produced by some wind turbine
Wind turbine
A wind turbine is a device that converts kinetic energy from the wind into mechanical energy. If the mechanical energy is used to produce electricity, the device may be called a wind generator or wind charger. If the mechanical energy is used to drive machinery, such as for grinding grain or...
s is believed by some to cause "wind-turbine syndrome" (headaches, dizziness, nausea) in humans and other animals close to the turbines, although there are "mixed opinions on whether wind turbines emit infrasound and if the amount is any more than that emitted by diesel engines or waves crashing on the beach."
Infrasonic 17 Hz tone experiment
On May 31, 2003, a team of UK researchers held a mass experiment where they exposed some 700 people to music laced with soft 17 Hz sine waves played at a level described as "near the edge of hearing", produced by an extra-long-stroke subwoofer mounted two-thirds of the way from the end of a seven-meter-long plastic sewer pipe. The experimental concert (entitled Infrasonic) took place in the Purcell RoomPurcell Room
The Purcell Room is a concert and performance venue which forms part of the Southbank Centre, one of central London's leading cultural complexes. It is named after the 17th century English composer Henry Purcell and has 370 seats....
over the course of two performances, each consisting of four musical pieces. Two of the pieces in each concert had 17 Hz tones played underneath. In the second concert, the pieces that were to carry a 17 Hz undertone were swapped so that test results would not focus on any specific musical piece. The participants were not told which pieces included the low-level 17 Hz near-infrasonic tone. The presence of the tone resulted in a significant number (22%) of respondents reporting anxiety, uneasiness, extreme sorrow, nervous feelings of revulsion or fear, chills down the spine and feelings of pressure on the chest. In presenting the evidence to British Association for the Advancement of Science
British Association for the Advancement of Science
frame|right|"The BA" logoThe British Association for the Advancement of Science or the British Science Association, formerly known as the BA, is a learned society with the object of promoting science, directing general attention to scientific matters, and facilitating interaction between...
, Professor Richard Wiseman
Richard Wiseman
Richard Wiseman is Professor of the Public Understanding of Psychology at the University of Hertfordshire in the United Kingdom.Wiseman started his professional life as a magician, before graduating in Psychology from University College London and obtaining a Ph.D...
said, "These results suggest that low frequency sound can cause people to have unusual experiences even though they cannot consciously detect infrasound. Some scientists have suggested that this level of sound may be present at some allegedly haunted sites and so cause people to have odd sensations
Apparitional experience
In psychology and parapsychology, an apparitional experience is an anomalous, quasi-perceptual experience.It is characterized by the apparent perception of either a living being or an inanimate object without there being any material stimulus for such a perception...
that they attribute to a ghost
Ghost
In traditional belief and fiction, a ghost is the soul or spirit of a deceased person or animal that can appear, in visible form or other manifestation, to the living. Descriptions of the apparition of ghosts vary widely from an invisible presence to translucent or barely visible wispy shapes, to...
—our findings support these ideas."
Suggested relationship to ghost sightings
Research by Vic TandyVic Tandy
Vic Tandy was a lecturer in Information Technology at Coventry University in Warwickshire and British engineer. He was best known for his research into the relationship between infrasound and ghostly apparitions....
, a lecturer at Coventry University
Coventry University
Coventry University is a post-1992 university in Coventry, West Midlands, England. Under the terms of the Further and Higher Education Act of 1992, the institution's name was changed from Coventry Polytechnic to Coventry University...
, suggested that an infrasonic signal of 19 Hz might be responsible for some ghost sightings
Apparitional experience
In psychology and parapsychology, an apparitional experience is an anomalous, quasi-perceptual experience.It is characterized by the apparent perception of either a living being or an inanimate object without there being any material stimulus for such a perception...
. Tandy was working late one night alone in a supposedly haunted laboratory at Warwick
Warwick
Warwick is the county town of Warwickshire, England. The town lies upon the River Avon, south of Coventry and just west of Leamington Spa and Whitnash with which it is conjoined. As of the 2001 United Kingdom census, it had a population of 23,350...
, when he felt very anxious and could detect a grey blob out of the corner of his eye. When Tandy turned to face the grey blob, there was nothing.
The following day, Tandy was working on his fencing
Fencing
Fencing, which is also known as modern fencing to distinguish it from historical fencing, is a family of combat sports using bladed weapons.Fencing is one of four sports which have been featured at every one of the modern Olympic Games...
foil
Foil (fencing)
A foil is a type of weapon used in fencing. It is the most common weapon in terms of usage in competition, and is usually the choice for elementary classes for fencing in general.- Components:...
, with the handle held in a vise
Vise (tool)
A vise or vice is a mechanical screw apparatus used for holding or clamping a work piece to allow work to be performed on it with tools such as saws, planes, drills, mills, screwdrivers, sandpaper, etc. Vises usually have one fixed jaw and another, parallel, jaw which is moved towards or away from...
. Although there was nothing touching it, the blade started to vibrate wildly. Further investigation led Tandy to discover that the extractor fan in the lab was emitting a frequency of 18.98 Hz, very close to the resonant frequency of the eye given as 18 Hz by NASA. This was why Tandy had seen a ghostly figure—it was an optical illusion caused by his eyeballs resonating. The room was exactly half a wavelength in length, and the desk was in the centre, thus causing a standing wave
Standing wave
In physics, a standing wave – also known as a stationary wave – is a wave that remains in a constant position.This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling...
which caused the vibration of the foil.
Tandy investigated this phenomenon further and wrote a paper entitled The Ghost in the Machine. Tandy carried out a number of investigations at various sites believed to be haunted, including the basement of the Tourist Information Bureau next to Coventry Cathedral
Coventry Cathedral
Coventry Cathedral, also known as St Michael's Cathedral, is the seat of the Bishop of Coventry and the Diocese of Coventry, in Coventry, West Midlands, England. The current bishop is the Right Revd Christopher Cocksworth....
and Edinburgh Castle
Edinburgh Castle
Edinburgh Castle is a fortress which dominates the skyline of the city of Edinburgh, Scotland, from its position atop the volcanic Castle Rock. Human habitation of the site is dated back as far as the 9th century BC, although the nature of early settlement is unclear...
.
See also
- BioacousticsBioacousticsBioacoustics is a cross-disciplinary science that combines biology and acoustics. Usually it refers to the investigation of sound production, dispersion through elastic media, and reception in animals, including humans. This involves neurophysiological and anatomical basis of sound production and...
- Brown noteBrown noteThe brown note is a theoretical infrasonic frequency that would cause humans to lose control of their bowels due to resonance. There is no scientific evidence to support the claim that a "brown note" exists....
- Clear-air turbulenceClear-Air TurbulenceClear air turbulence is the turbulent movement of air masses in the absence of any visual cues such as clouds, and is caused when bodies of air moving at widely different speeds meet....
- Demonstrated infrasonic weapon
- Helmholtz resonanceHelmholtz resonanceHelmholtz resonance is the phenomenon of air resonance in a cavity, such as when one blows across the top of an empty bottle. The name comes from a device created in the 1850s by Hermann von Helmholtz, the "Helmholtz resonator", which he, the author of the classic study of acoustic science, used to...
- MicrobaromMicrobaromIn acoustics, microbaroms, also known as the "voice of the sea",are a class of atmospheric infrasonic waves generated in marine stormsby a non-linear interaction of ocean surface waves with the atmosphere....
- The HumThe HumThe Hum is a generic name for a series of phenomena involving a persistent and invasive low-frequency humming noise not audible to all people. Hums have been reported in various geographical locations. In some cases a source has been located. A Hum on the Big Island of Hawaii, typically related...
- UltrasoundUltrasoundUltrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
External links
- Inframatics, an international infrasound monitoring organization
- NOAA Infrasonics Program
- US Army Space and Missile Defense Command Monitoring Research Program
- Los Alamos Infrasound Monitoring Laboratory
- Infrasonic and Acoustic-Gravity Waves Generated by the Mount Pinatubo Eruption of June 15, 1991, Makoto Tahira, Masahiro Nomura, Yosihiro Sawada and Kosuke Kamo