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  Infrasound Infrasound  is sound that is lower in frequency than 20 Hz (Hertz) or cycles per second, the normallimit 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 primaryorgan 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 earthquakes , 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 tocover long distances and get around obstacles with little dissipation .Infrasound - Wikipedia, the free encyclopedia About infrasound Possibly the first observation of naturally occurring infrasound was in the aftermath of the 1883 eruption of Krakatoa , when concussive acoustic waves circled the globe seven times or more and were recorded on barometers worldwide. Infrasound was also used by Allied forces in World War I  to locate artillery . 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 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 and soon got to work preparing tests in the labs. One of his experiments was an infrasoni! histle . [# [3 [$ Infrasound sometimes results naturally from severe eather ,  surf , [%   lee aves , avalan!hes , earthquakes , vol!anoes , &olides , ['   aterfalls , !alvin(  of i!e&er(s , aurora , li(htnin( and upper)atmospheri! li(htnin( . [*   +onlinear   o!ean ave  interactions in ocean storms produce pervasive infrasound vibrations around 0.2 Hz, known as mi!ro&aroms . [8 Infrasound can also be generated by man-made processes such as soni! &ooms  and e,plosions  (both chemical and  nu!lear ), by machinery such as  diesel en(ines  and older designs of down tower ind tur&ines  and by specially designed mechanical transducers (industrial vibration tables) and large-scale su& oofer  loudspeakers. [-  The .omprehensive +u!lear)/est)0an /reaty r(anization  uses infrasound as one of its monitoring technologies (along with seismi! , hydroa!ousti! , and  atmospheri! radionu!lide monitoring). Whales , elephants ,  hippopotamuses ,  rhino!eros , (iraffes ,  okapi , and  alli(ators  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 &irds  use naturally generated infrasound, from sources such as turbulent airflow over  mountain  ranges, as a navi(ational  aid. [12  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.Scientists accidentally discovered that the spinning core or vortex of a tornado  creates infrasonic waves. When the vortices are large, the frequencies are lower; smaller vortices have higher, thoughstill infrasonic, frequencies. These low frequency sound waves can be detected for up to 160 kilometres (100 mi) away and can help provide early warning of tornadoes.A number of American universities have active research programs in infrasound, including the niversity of 4ississippi , 5outhern 4ethodist niversity , the  niversity of .alifornia at 5an 6ie(o , the niversity of 7laska air&anks , and the niversity of Ha aii at 4anoa .  [ edit ]Animal reactions to infrasound Animals have been known to perceive the infrasonic waves carried through the earth by natural disasters and can use these as an early warning. A recent example of this is the #22$ Indian !ean earthquake and tsunami . Animals were reported to flee the area long before the actual tsunami hit the shores of Asia. [11  It is not known for sure if this is the exact reason, as some have suggested that it was the influence of ele!troma(neti! aves , and not of infrasonic waves, that prompted these animals to flee. [1# Infrasound may also be used for long-distance communication in 7fri!an elephants . [13  These calls range from 15–35 Hz and can be as loud as 117 d0 , allowing communication for many kilometres, with a possible maximum range of around 10 km (6 mi). [1$  These calls may be used to coordinate the movement of herds and allow male elephants to find mates. [ edit ]Human reactions to infrasound When testing human hearing, pure sine wave tones are perceived as less musical near the bottom of the hearing range. Between 10 Hz and 20 Hz, such tones cease being heard as a musical tone unlessthey are boosted greatly in volume. [1%  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  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. [1' [1*  Since it is not consciously perceived, it can make people feel vaguely that supernatural  events are taking place.Some  film  soundtracks make use of infrasound to produce unease or disorientation in the audience.  Irréversible  is one such movie.The infrasound and low-frequency noise produced by some ind tur&ines  is believed to cause certain breathing and digestive problems in humans and other animals in close proximity to the turbines. [18 [ edit ]  Infrasonic  17 Hz tone experiment On May 31, 2003, a team of UK researchers held a mass experiment where they exposed some 700people 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 sub-woofer mounted two-thirds of the way from the endof a seven-meter-long plastic sewer pipe. The experimental concert (entitled  Infrasonic ) took place in the 9ur!ell :oom  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. [1- [#2  In presenting the evidence to  0ritish 7sso!iation for the 7dvan!ement of 5!ien!e , one of the scientists 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 (host —our findings support these ideas. [ edit ] The Ghost in the Machine Research by Vi! /andy , a lecturer at .oventry niversity , suggested that the frequency 19 Hz was responsible for many ghost sightings. He was working late one night alone in a supposedly haunted  laboratory at War i!k , when he felt very anxious and could detect a grey blob out of the corner of his eye. When he turned to face it, there was nothing.The following day, he was working on his fencing foil , with the handle held in a vice. Although there was nothing touching it, the blade started to vibrate wildly. Further investigation led him to discover that the extraction fan was emitting a frequency of 18.98 Hz, very close to the  resonant frequen!y  of the eye (given as 18 Hz in NASA Technical Report 19770013810). This was why he saw 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 standin( ave  which was detected by the foil. [#1 Tandy investigated this phenomenon further and wrote a paper entitled The Ghost in the Machine . He 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  ;din&ur(h .astle . [#3 [ #$  References 1. ^   .hapter 8 <6eadly 5ounds< = 6r> Vladimir Gavreau <?ost 5!ien!e< &y Gerry Vassilatos I50+ 2)-3#813)*%)% @ 1--- 5IG+7?5 2. ^  *Gavreau V., Infra Sons: G é n é rateurs, D é tecteurs, Propri é t é s physiques, Effets biologiques, in: Acustica, Vol .17, No. 1 (1966), p.1–103. ^  Gavreau V.,infrasound,in: science journal 4(1) 1968,S.334. ^  Gavreau V., Sons graves intenses et infrasons in: Scientific Progres – la Nature (Sept. 1968) p. 336–3445. ^  Garces, M.; Hetzer C., Merrifield M., Willis M. and Aucan J. (2003). Observations of surf infrasound in Hawai’i . Retrieved 2007-12-15. Comparison of ocean buoy measurements with infrasonic array data collected during the epic winter of 2002–2003 shows a clear relationship between breaking ocean wave height and infrasonic signal levels. .6. ^  Garces, M.; Willis, M. (2006).  Modeling and Characterization of Microbarom Signals in the Pacific . Retrieved 2007-11-24. Naturally occurring sources of infrasound include (but are not limited to) severe weather, volcanoes, bolides, earthquakes, surf, mountain waves, and, the focus of this research, nonlinear ocean wave interactions. .7. ^  Haak, Hein (2006-09-01). 9ro&in( the 7tmosphere ith Infrasound A Infrasound as a tool (pdf). CTBT: Synergies with Science, 1996–2006 and Beyond  . Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization. Retrieved 2007-11-24.8. ^   4i!ro&aroms .  Infrasonic Signals .  niversity of 7laska air&anks , Geophysical Institute, Infrasound Research Group. Retrieved 2007-11-22. The ubiquitous five second period infrasonic signals called “microbaroms”, which are generated by standing sea waves in marine storms, are the cause of the low-level natural-infrasound background in the passband from 0.02 to 10 Hz. 9. ^  Chen, C.H., ed (2007). Signal and Image Processing for Remote Sensing . Boca Raton: CRC. pp. 33.  I50+   2)8$-3)%2-1)3 .10. ^   Goddard 5pa!e li(ht .enter [ dead link  ]11. ^   Ho did animals survive the tsunamiB ) 0y .hristine Kenneally ) 5late 4a(azineA9osted /hursdayC 6e!> 32C #22$C at %A$* 94 ;/ 12. ^   +ature > .an 7nimals 9redi!t 6isasterB ) 905A posted +ovem&er #22%> 13. ^  Langbauer, W.R.; Payne, K.B.; Charif, R.A.; Rapaport, L.; Osborn, F. (1991), 7fri!an elephants respond to distant play&a!ks of lo )frequen!y !onspe!ifi! !alls ,  Journal of Experimental Biology   157 (1): 35–46, retrieved 2009-05-2714. ^  Larom, D.; Garstang, M.; Payne, K.; Raspet, R.; Lindeque, M. (1997), /he  influen!e of surfa!e atmospheri! !onditions on the ran(e and area rea!hed &y animal vo!alizations ,  Journal of experimental biology   200  (3): 421–431, retrieved 2009-05-2715. ^   lsonC Harry >  (1967).   Music Ph!sics and ngineering . Dover Publications. p. 249.  I50+   2$8'#1*'-8 .16. ^   Dohn 6> .ody>  Infrasound  Borderland Science Research Foundation17. ^  V. Tandy & T. Lawrence - 'The ghost in the machine', Journal of the Society for Psychical Research #62, pp.360–364. 1998. AND S. Angliss, GeNIA, C. O'Keeffe, R. Wiseman & R. Lord - 'Soundless music', in B. Arends & D. Thackara (eds), Experiments: Conversations in art and science, pp.139–71. The Wellcome Trust: London, 2003. Quote from R. Wiseman, Quirkology - How We Discover the Big Truths in Small Things , Basic Books, 200718. ^   Ho 5tuffWorks>  #o wind turbines cause health $roblems% 19. ^    Infrasonic  concert, Purcell Room, London, 31 May, 2003, sponsored by the sciart Consortium  with additional support by the +ational 9hysi!al ?a&oratory E+9?F 20. ^   Sounds like terror in the air  5ydney 4ornin( HeraldC 5eptem&er -  2003.21. ^   infrasound 22. ^   Guardian nlimited 7r!hive 5ear!h 23. ^   Who ya (onna !allB Vi! /andy ) .oventry /ele(raph 24. ^   Internet 7r!hive Way&a!k 4a!hine> #22* version of Vi! /andys Ghost ;,periment e&pa(e ã infrasound . Collins English Dictionary , 2000. Retrieved 25 October 2005, from xreferplus. httpA >,referplus>!omentry#'%*-$- ã Gundersen, P. Erik. The Handy Physics Answer Book  . Visible Ink Press, 2003. ã Chedd, Graham. Sound; From Communications to Noise Pollution . Doubleday & CompanyInc, 1970. ã 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. 132–133. ã  Discovery's Biggest Shows aired   at 8:00 pm (Indian Standard Time) on The Discovery Channel, India on Sunday, 7 October 2007 By John D. CodyAS thunderous tones deepen, their power seemingly intensifies over frail barriers such as glass windows. Certain abrupt thunder peals often shatter windows into tiny fragments. In the apparent absence of thunderous tones we may observe the strong and continuous vibration of glass window panes during storms. A sudden eerie silence, and the window is shattered before our eyes.atural phenomena are prodigious generators of infrasound. !he potent distal effects produced when natural e plosions occur produce legendary effects. #hen $ra%atoa e ploded, windows were shattered hundreds of miles away by the infrasonic wave. #indwas not the causative agent of these occurrences, as no wind was felt or detected. Seismographic stations registered the blast, and barometers measured the shoc%waves. !he &ringing& of both earth and atmosphere continued for hours. It is believed that

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Jul 23, 2017
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