Infrasound is sound with a frequency too low to be detected by the human ear. The study of such sound waves is sometimes referred to as infrasonics, covering sounds from the lower limit of human hearing (about 16 or 17 hertz) down to 0.001 hertz. This frequency range is the same one that seismographs use for monitoring earthquakes. Infrasound is characterized by an ability to cover long distances and get around obstacles with little dissipation. Possibly the first observation of naturally-occurring infrasound was in the aftermath of the Krakatoa eruption in 1883, when concussive acoustic waves circled the globe seven times or more and were recorded on barometers worldwide. Sound is a disturbance of mechanical energy that propagates through matter as a wave. ... Sine waves of various frequencies; the bottom waves have higher frequencies than those above. ... Bat ears come in different sizes and shapes The ear is the sense organ that detects sound. ... The hertz (symbol: Hz) is the SI unit of frequency. ... Seismographs (in Greek seismos = earthquake and graphein = write) are used by seismologists to record seismic waves. ... An earthquake is a phenomenon that results from and is powered by the sudden release of stored energy in the crust that propagates seismic waves. ... Krakatoa (Indonesian name: Krakatau, Portuguese name: Krakatao) is a volcanic island in the Sunda Strait between Java and Sumatra in Indonesia. ...

One of the pioneers in infrasonic research was French scientist Vladimir Gavreau, born in Russia as Vladimir Gavronsky. [1] His interest in infrasonic waves first came about in his lab during the 1960's where 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 and soon got to work preparing tests in the labs. One of his experiments was an infrasonic whistle. ^[1][2][3] The tympanum or tympanic membrane, colloquially known as eardrum, is a thin membrane that separates the outer ear from the middle ear. ...

Infrasound sometimes results naturally from ocean waves, avalanches, earthquakes, volcanoes, and meteors. Infrasound can also be generated by man-made processes such as explosions, both chemical and nuclear. The Comprehensive Nuclear-Test-Ban Treaty Organization uses infrasound as one of its monitoring technologies (along with seismic, hydroacoustic, and atmospheric radionuclide monitoring). Ocean waves Ocean surface waves are surface waves which occur at the surface of an ocean. ... A Himalayan avalanche. ... An earthquake is a phenomenon that results from and is powered by the sudden release of stored energy in the crust that propagates seismic waves. ... Volcano 1. ... Photo of a burst of meteors with extended exposure time A meteor is the visible path of a meteoroid that enters the Earths (or another bodys) atmosphere, commonly called a shooting star or falling star. ... It has been suggested that Nuclear explosive be merged into this article or section. ... Comprehensive Test Ban Treaty Opened for signature September 10, 1996[1] in New York Entered into force Not yet in force Conditions for entry into force The treaty will enter into force 180 days after it is ratified by all of the following 44 (Annex 2) countries: Algeria, Argentina, Australia... Seismology (from the Greek seismos = earthquake and logos = word) is the scientific study of earthquakes and the movement of waves through the Earth. ... A hydrophone is a sound-to-electricity transducer for use in water or other liquids, analogous to a microphone for air. ... A radionuclide is an atom with an unstable nucleus. ...

Whales, elephants, rhinoceros, giraffes, okapi, and alligators are known to use infrasound to communicate over varying distances of up to many miles as in the case of the whale, for instance. It has also been suggested [2] that migrating birds use naturally generated infrasound, from sources such as turbulent airflow over mountain ranges, as a navigational aid. A Fin whale The term whale is ambiguous: it can refer to all cetaceans, to just the larger ones, or only to members of particular families within the order Cetacea. ... For other uses, see Elephant (disambiguation). ... Genera Ceratotherium Dicerorhinus Diceros Rhinoceros Coelodonta (extinct) Elasmotherium (extinct) The rhinoceros (commonly called rhino for short; plural can be either rhinoceros or rhinoceroses) is any of five surviving species of odd-toed ungulates in the family Rhinocerotidae. ... Binomial name Giraffa camelopardalis Linnaeus, 1758 The Giraffe (Giraffa camelopardalis) is an African even-toed ungulate mammal, the tallest of all land-living animal species. ... Binomial name Okapia johnstoni (P.L. Sclater, 1901) Okapi distribution The okapi (Okapia johnstoni) is a mammal of the Ituri Rainforest in central Africa. ... Species Alligator mississippiensis Alligator sinensis An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. ... Orders Many - see section below. ... A mountain is a landform that extends above the surrounding terrain in a limited area. ... Table of geography, hydrography, and navigation, from the 1728 Cyclopaedia. ...

Scientists discovered by accident that the spinning core or vortex of a tornado creates infrasonic sounds. When the vortices are large, the frequencies are lower; smaller vortices have higher frequencies. These infrasonic sound waves can be detected for up to 161km (100 miles) away, and so can help provide early warning of tornadoes. A tornado in central Oklahoma. ...

Concerning behavioral patterns of animals and the infrasonic effects of natural disasters, it is to be noted that animals can also recognize the infrasonic waves emitted from such natural disasters and can use these as an early warning. A very important example of this is the 2004 Indian Ocean earthquake. Animals were reported to flee the area long before the actual tsunami hit the shores of Asia.[3] 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.[4] The tsunami caused by the December 26, 2004 earthquake strikes Ao Nang, Thailand. ... Electromagnetic radiation or EM radiation is a combination (cross product) of oscillating electric and magnetic fields perpendicular to each other, moving through space as a wave, effectively transporting energy and momentum. ...

It has long been realized that infrasound may cause feelings of awe or fear. Since it is not consciously perceived, it can make people feel vaguely that supernatural events are taking place. In a controlled experiment published in September, 2003, people at a concert were asked to rate their responses to a variety of pieces of music, some of which were accompanied by infrasonic elements. The participants were not aware of which pieces included the infrasound. Many participants (22%) reported feelings of anxiety, uneasiness, extreme sorrow, nervous feelings of revulsion or fear and chills down the spine which correlated with the infrasonic events. In presenting the evidence to the BA, the scientist responsible 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". Look up Supernatural in Wiktionary, the free dictionary. ... 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... The British Association or the British Association for the Advancement of Science or the BA is a learned society with the object of promoting science, directing general attention to scientific matters, and facilitating intercourse between scientific workers. ...

Some film soundtracks also make use of infrasound to produce unease or disorientation in the audience. Irréversible is one such movie. Film is a term that encompasses motion pictures as individual projects, as well as the field in general. ... Irréversible (2002, France) is a film written, directed, edited, and photographed by Gaspar Noé. It is considered to be one of the most disturbing and controversial films of 2002, due to its explicit on-camera depiction of rape and murder. ...

In music, Brian "Lustmord" Williams is known to utilize infrasound to create these same feelings. Music is a form of art and entertainment or other human activity that involves organized and audible sounds and silence. ... Brian Lustmord Williams is a musician credited with creating the dark ambient genre with the influential album, Heresy - a relentlessly dark work that sounds like a journey through Hell. ...

References

• infrasound. Collins English Dictionary (2000). Retrieved 25 October 2005, from xreferplus. http://www.xreferplus.com/entry/2657949
• Gundersen, P. Erik. The Handy Physics Answer Book. Visible Ink Press, 2003.
• Chedd, Graham. Sound; From Communications to Noise Pollution. Doubleday & Company Inc, 1970.
• O'Keefe, Ciaran, and Sarah Angliss. "The Subjective Effects of Infrasound in a Live Concert Setting." CIM04: Conference on Interdisciplinary Musicology. Graz, Germany: Graz UP, 2004. 132-3.

1. ^ *Gavreau V., Infra Sons: Générateurs, Détecteurs, Propriétés physiques, Effets biologiques, in: Acustica, Vol .17, No. 1 (1966), p.1-10
2. ^ Gavreau V.,infrasound,in: science journal 4(1) 1968,S.33
3. ^ Gavreau V., "Sons graves intenses et infrasons" in: Scientific Progres – la Nature (Sept. 1968) p. 336-344

External links

• Infrasound: Air Seismology - from About.com
• Acoustic weapons disorient rioters and afflicts an invading army with nausea
• Boom car noise is an offense to homeowners and recreation seekers
• An article about supposed infrasonic weapons
• Inframatics, an international infrasound monitoring organization
• National Center for Physical Acoustics
• Infrasound Laboratory, University of Hawaii
• Southern Methodist University infrasound studies
• NOAA Infrasonics Program
• US Army Space and Missile Defense Command Monitoring Research Program
• Laboratory for Atmospheric Acoustics, University of California, San Diego
• Los Alamos Infrasound Monitoring Laboratory
• University of Alaska Infrasonics Page
• Infrasonic and Acoustic-Gravity Waves Generated by the Mount Pinatubo Eruption of June 15, 1991, Makoto Tahira, Masahiro Nomura, Yosihiro Sawada and Kosuke Kamo
• Deadly Sounds — Dr. Vladimir Gavreau
• How did animals survive the Tsunami?
• Can animals predict disaster?