Editing Infrasound

{{Short description|Vibrations with frequencies lower than 20 hertz}}
{{Use dmy dates|date=October 2020}}
[[File:Infrasound Arrays.jpg|thumb|upright=1.5|Infrasound arrays at monitoring station in [[Qaanaaq]], [[Greenland]].]]

'''Infrasound''', sometimes referred to as '''low frequency sound''' or incorrectly '''subsonic''' (subsonic being a descriptor for "less than the speed of sound"),<ref>https://dictionary.cambridge.org/us/dictionary/english/subsonic</ref> describes sound waves with a [[Audio frequency|frequency]] below the lower limit of human audibility (generally 20 [[Hertz|Hz]], as defined by the [[ANSI/ASA S1.1-2013]] standard).<ref>{{cite web|url=https://ia.cpuc.ca.gov/environment/info/dudek/ecosub/E1/D.8.2_AStudyofLowFreqNoiseandInfrasound.pdf|title=A Study of Low Frequency Noise and Infrasound from Wind Turbines|website=Ia.cpuc.ca.gov|access-date=12 March 2022}}</ref> Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the [[sound pressure]] must be sufficiently high. Although the ear is the primary organ for sensing low sound, at higher intensities 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&nbsp;Hz down to 0.1&nbsp;Hz (and rarely to 0.001&nbsp;Hz). People use this frequency range for monitoring earthquakes and volcanoes, charting rock and petroleum formations below the earth, and also in [[ballistocardiography]] and seismocardiography to study the mechanics of the human cardiovascular system.

Infrasound is characterized by an ability to get around obstacles with little [[dissipation]]. In [[music]], [[waveguide (acoustics)|acoustic waveguide]] methods, such as a large [[pipe organ]] or, for reproduction, exotic loudspeaker designs such as [[Transmission line loudspeaker|transmission line]], [[rotary woofer]], or traditional [[subwoofer]] designs can produce low-frequency sounds, including near-infrasound. Subwoofers designed to produce infrasound are capable of sound reproduction an octave or more below that of most commercially available subwoofers, and are often about 10 times the size.{{citation needed |date=February 2018}}

== History and study ==
One of the pioneers in infrasonic research was French scientist [[Vladimir Gavreau]].<ref name=":0">[http://www.hbci.com/~wenonah/history/gavreau.htm "Gavreau", in ''Lost Science''] {{webarchive |url=https://web.archive.org/web/20120219172757/http://www.hbci.com/~wenonah/history/gavreau.htm |date=19 February 2012 }} by Gerry Vassilatos. Signals, 1999. {{ISBN|0-932813-75-5}}</ref> His interest in infrasonic waves first came about in 1957 in the large concrete building that he and his research team were working in. The group was experiencing bouts of periodic and deeply unpleasant nausea. After weeks of speculation on the source of the nausea&nbsp;— the team was convinced that it was a pathogen or an untraced leak of noxious chemical fumes in the facility&nbsp;— they discovered that a "loosely poised low speed motor... was developing [these] 'nauseating vibrations'".<ref name=":0" />

When Gavreau and the team attempted to measure an amplitude and pitch, they were shocked when their equipment detected no audible sound. They concluded the sound being generated by the motor was so low in pitch that it was below their biological ability to hear, and that their recording equipment was not capable of detecting these frequencies. Nobody had conceived that sound might exist at such low frequencies, and so no equipment had been developed to detect it. Eventually, it was determined that the sound inducing the nausea was a 7 cycle per second infrasound wave that was inducing a resonant mode in the ductwork and architecture of the building, significantly amplifying the sound.<ref name=":0" /> In the wake of this serendipitous discovery, the researchers soon got to work preparing further infrasonic tests in the laboratories. One of his experiments was an infrasonic whistle, an oversized [[organ pipe]].<ref>Gavreau V., Infra Sons: Générateurs, Détecteurs, Propriétés physiques, Effets biologiques, in: Acustica, vol. 17, no. 1 (1966), pp. 1–10</ref><ref>Gavreau V., infrasound, in: Science journal 4(1) 1968, p. 33</ref><ref>Gavreau V., "Sons graves intenses et infrasons" in: Scientific Progress&nbsp;– la Nature (Sept. 1968) pp. 336–344</ref> As a result of this and similar incidents, it has become routine in new architecture construction to inspect for and eliminate any infrasonic resonances in cavities and the introduction of sound-proofing and materials with specialized sonic properties.

== Sources ==
[[File:Graham Holliman Velocity-Coupled Infra Bass speaker design.jpg|thumb|upright=1.2|Patent for a double bass reflex [[loudspeaker enclosure]] design intended to produce infrasonic frequencies ranging from 5 to 25 hertz, of which traditional [[subwoofer]] designs are not readily capable.]]
Infrasound can result from both natural and man-made sources:

:* Natural events: infrasonic sound sometimes results naturally from [[severe weather]], [[Ocean surface wave|surf]],<ref name=Garces2003>{{cite journal| author = Garces, M.| author2 = Hetzer C.| author3 = Merrifield M.| author4 = Willis M.| author5 = Aucan J.| year = 2003| pages = 2264| issue = 24| volume = 30| title = Observations of surf infrasound in Hawai'i| journal = Geophysical Research Letters| doi = 10.1029/2003GL018614| quote = 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.| bibcode = 2003GeoRL..30.2264G| s2cid = 42665337| doi-access = free}}</ref> [[lee wave]]s, [[avalanche]]s, [[earthquake]]s, [[volcano]]es,<ref>{{Cite journal|last1=Fee|first1=David|last2=Matoza|first2=Robin S.|date=2013-01-01|title=An overview of volcano infrasound: From hawaiian to plinian, local to global|url=http://www.sciencedirect.com/science/article/pii/S0377027312002685|journal=Journal of Volcanology and Geothermal Research|language=en|volume=249|pages=123–139|doi=10.1016/j.jvolgeores.2012.09.002|bibcode=2013JVGR..249..123F|issn=0377-0273|url-access=subscription}}</ref><ref>{{Cite journal|last1=Johnson|first1=Jeffrey Bruce|last2=Ripepe|first2=Maurizio|date=2011-09-15|title=Volcano infrasound: A review|url=http://www.sciencedirect.com/science/article/pii/S0377027311001727|journal=Journal of Volcanology and Geothermal Research|language=en|volume=206|issue=3|pages=61–69|doi=10.1016/j.jvolgeores.2011.06.006|bibcode=2011JVGR..206...61J|issn=0377-0273|url-access=subscription}}</ref> [[bolide]]s,<ref name="Garces2006">{{cite report | author = Garces, M.| author2 = Willis, M.| year = 2006| title = Modeling and Characterization of Microbarom Signals in the Pacific| url = http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA456958| access-date = 24 November 2007| quote = Naturally occurring sources of infrasound include (but are not limited to) severe weather, volcanoes, bolides, earthquakes, mountain waves, surf, and, the focus of this research, nonlinear ocean wave interactions.| archive-url = https://web.archive.org/web/20090211172356/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA456958| archive-date = 11 February 2009| url-status = dead}}</ref> [[waterfall]]s, [[Ice calving|calving]] of [[iceberg]]s, [[Aurora (astronomy)|aurorae]], [[meteor]]s, [[lightning]] and [[upper-atmospheric lightning]].<ref name="title">{{cite web|url=http://www.ctbto.org/reference/symposiums/2006/haak/0901probingtheatmosphere.pdf | author = Haak, Hein |title=Probing the Atmosphere with Infrasound : Infrasound as a tool | date=  1 September 2006 | publisher = Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization|work= CTBT: Synergies with Science, 1996–2006 and Beyond |archive-url = https://web.archive.org/web/20070702200640/http://www.ctbto.org/reference/symposiums/2006/haak/0901probingtheatmosphere.pdf |archive-date = 2 July 2007}}</ref> [[Nonlinear]] [[ocean surface wave|ocean wave]] interactions in ocean storms produce pervasive infrasound vibrations around 0.2&nbsp;Hz, known as [[microbarom]]s.<ref name=GI>{{cite web |url=http://www.gi.alaska.edu/infrasound/Infrasound254.htm |title=Microbaroms |access-date=22 November 2007 |publisher=[[University of Alaska Fairbanks]], Geophysical Institute, Infrasound Research Group |work=Infrasonic Signals |quote=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&nbsp;Hz. |archive-url=https://web.archive.org/web/20080215074429/http://www.gi.alaska.edu/infrasound/Infrasound254.htm |archive-date=15 February 2008 |url-status=dead}}</ref> According to the Infrasonics Program at [[National Oceanic and Atmospheric Administration|NOAA]], infrasonic arrays can be used to locate avalanches in the Rocky Mountains, and to detect [[tornado]]es on the high plains several minutes before they touch down.<ref>{{cite web|url=http://www.esrl.noaa.gov/psd/programs/infrasound/|title=NOAA ESRL Infrasonics Program|access-date=10 April 2012|archive-url=https://web.archive.org/web/20200408192005/https://psl.noaa.gov/programs/infrasound/|archive-date=8 April 2020|url-status=live}}</ref>

:* Animal communication: [[whales]], [[elephants]],<ref>{{cite journal | last1 = Payne | first1 = Katharine B. | author-link = Katharine Payne | last2 = Langbauer | first2 = William R. | last3 = Thomas | first3 = Elizabeth M. | year = 1986 | title = Infrasonic calls of the Asian elephant (Elephas maximus) | journal = Behavioral Ecology and Sociobiology | volume = 18 | issue = 4| pages = 297–301 | doi = 10.1007/BF00300007 | s2cid = 1480496 }}</ref> [[hippopotamus]]es,<ref>{{cite journal | last1 = Barklow | first1 = William E. | year = 2004 | title = Low-frequency sounds and amphibious communication in Hippopotamus amphibious | url = http://asadl.org/jasa/resource/1/jasman/v115/i5/p2555_s1?bypassSSO=1 | journal = Journal of the Acoustical Society of America | volume = 115 | issue = 5 | pages = 2555 | doi = 10.1121/1.4783854 | bibcode = 2004ASAJ..115.2555B | url-status = dead | archive-url = https://web.archive.org/web/20130208150037/http://asadl.org/jasa/resource/1/jasman/v115/i5/p2555_s1?bypassSSO=1 | archive-date = 8 February 2013| url-access = subscription }}</ref> [[rhinoceros]]es,<ref>{{cite book |last1=von Muggenthaler |first1=E.K. |last2=Stoughton |first2=J.W. |last3=Daniel |first3=((J.C., Jr.)) |date=1993 |title=Rhinoceros biology and conservation: Proceedings of an international conference, San Diego, U.S.A |chapter=Infrasound from the rhinocerotidae |chapter-url=http://www.rhinoresourcecenter.com/index.php?act=refs&CODE=ref_detail&id=1165238239 |editor-last=Ryder |editor-first=O.A. |publisher=Zoological Society of San Diego |pages=136–140}}</ref><ref name="von-muggenthaler-2003">{{cite journal | doi = 10.1121/1.1588271 | volume=4 | title=Songlike vocalizations from the Sumatran Rhinoceros (Dicerorhinus sumatrensis) | year=2003 | journal=Acoustics Research Letters Online | page=83 | last = von Muggenthaler | first = Elizabeth| issue=3 | doi-access=free }}</ref><ref>{{cite conference |last=Marrin |first=West |date=3 November 2004 |title=Infrasonic signals in the environment |conference=Acoustics 2004: Transportation Noise & Vibration — The New Millennium |publisher=Australian Acoustical Society |location=Gold Coast, Australia |url=http://www.watersciences.org/documents/Infrasound-Marrin.pdf |url-status=dead |archive-url=https://web.archive.org/web/20120326095047/http://www.watersciences.org/documents/Infrasound-Marrin.pdf |archive-date=26 March 2012}}</ref> [[giraffes]],<ref>{{cite conference |last1=von Muggenthaler |first1=E. |last2=Baes |first2=C. |last3=Hill |first3=D. |last4=Fulk |first4=R. |last5=Lee |first5=A. |date=1999 |title=Infrasound and low frequency vocalizations from the giraffe; Helmholtz resonance in biology |conference=Riverbanks Consortium on biology and behavior |url=http://www.animalvoice.com/giraffe.htm |url-status=dead |archive-url=https://web.archive.org/web/20120215233027/http://www.animalvoice.com/giraffe.htm |archive-date=15 February 2012}}</ref> [[okapi]]s,<ref>E. Von Muggenthaler: ''Infrasound from the okapi'', invited presentation, student competition award, proceedings from the 1992 American Association for the Advancement of Science (A.A.A.S) 158th conference, 1992</ref> [[peacock]]s,<ref>{{Cite journal|last1=Freeman|first1=Angela R.|last2=Hare|first2=James F.|date=2015-04-01|title=Infrasound in mating displays: a peacock's tale|url=http://www.sciencedirect.com/science/article/pii/S0003347215000391|journal=Animal Behaviour|language=en|volume=102|pages=241–250|doi=10.1016/j.anbehav.2015.01.029|s2cid=53164879|issn=0003-3472|url-access=subscription}}</ref> and [[alligator]]s are known to use infrasound to communicate over distances—up to hundreds of miles in [[Whale sound|the case of whales]]. In particular, the [[Sumatran rhinoceros]] has been shown to produce sounds with frequencies as low as 3&nbsp;Hz which have similarities with the [[Whale song#Song of the humpback whale|song of the humpback whale]].<ref name="von-muggenthaler-2003" /> The [[Roar (utterance)|roar]] of the [[tiger]] contains infrasound of 18&nbsp;Hz and lower,<ref>Work by Muggenthaler et al, also referred to in: [https://www.sciencedaily.com/releases/2000/12/001201152406.htm ''The Secret Of A Tiger's Roar''], ScienceDaily, 1 December 2000, American Institute of Physics, Inside Science News Service (1 December 2000), Retrieved 25 December 2011</ref> and the [[purr]] of [[Felidae|felines]] is reported to cover a range of 20 to 50&nbsp;Hz.<ref>Von Muggenthaler, E., Perera, D. (2002), The cat's purr: a healing mechanism?, In review, presented 142nd Acoustical Society of America International Conference, 2001.</ref><ref>Work by Muggenthaler et al, referred to in: David Harrison: [https://www.telegraph.co.uk/news/worldnews/northamerica/usa/1326953/Revealed-how-purrs-are-secret-to-cats-nine-lives.html ''Revealed: how purrs are secret to cats' nine lives''], The Telegraph, 18 March 2001, Retrieved 25 December 2011</ref><ref>von Muggenthaler, (2006) The Felid Purr: A Biomechanical Healing Mechanism, Proceedings from the 12th International Low Frequency Noise and Vibration Conference, pp. 189–208</ref> It has also been suggested that migrating birds use naturally generated infrasound, from sources such as [[turbulent]] airflow over mountain ranges, as a [[navigation]]al aid.<ref>{{Cite web |url=http://pao.gsfc.nasa.gov/gsfc/educ/science/2000/04-07-00.htm |title=Science Question of the Week - 07 April 2000 |date=2 November 2004 |website= |access-date=12 March 2022 |archive-url=https://web.archive.org/web/20041102004955/http://pao.gsfc.nasa.gov/gsfc/educ/science/2000/04-07-00.htm |archive-date=2 November 2004 |url-status=dead}}</ref> Infrasound also may be used for long-distance communication, especially well documented in [[baleen whale]]s (see [[whale vocalization]]), and [[African elephant]]s.<ref>{{Cite journal| title = African elephants respond to distant playbacks of low-frequency conspecific calls| url = http://jeb.biologists.org/cgi/reprint/157/1/35.pdf| year = 1991| journal = The Journal of Experimental Biology| pages = 35–46| volume = 157| issue = 1| last1 = Langbauer| first1 =  W.R.| last2 =  Payne | first2 =  K.B.| last3 =  Charif | first3 =  R.A.| last4 =  Rapaport | first4 =  L.| last5 =  Osborn | first5 =  F.| doi = 10.1242/jeb.157.1.35| access-date =27 May 2009}}</ref> The frequency of baleen whale sounds can range from 10 [[Hertz|Hz]] to 31&nbsp;kHz,<ref name=RGMT>{{cite book |title=Marine Mammals and Noise |author1=W. John Richardson |author2=Charles R. Greene, Jr. |author3=Charles I. Malme |author4=Denis H. Thomson |year=1995 |publisher=Academic Press |isbn=978-0-12-588440-2}}</ref> and that of elephant calls from 15&nbsp;Hz to 35&nbsp;Hz. Both can be extremely loud (around 117&nbsp;[[Decibel|dB]]), allowing communication for many kilometres, with a possible maximum range of around {{convert|10|km|0|abbr=on}} for elephants,<ref>{{Cite journal| url = http://jeb.biologists.org/cgi/reprint/200/3/421.pdf| title = The influence of surface atmospheric conditions on the range and area reached by animal vocalizations| year = 1997| journal = [[The Journal of Experimental Biology]]| pages = 421–431| volume = 200| issue = 3| last1 = Larom | first1 =  D.| last2 =  Garstang | first2 =  M.| last3 =  Payne | first3 =  K.| last4 =  Raspet | first4 =  R.| last5 =  Lindeque | first5 =  M.| doi = 10.1242/jeb.200.3.421| pmid = 9057305| access-date =27 May 2009}}</ref> and potentially hundreds or thousands of kilometers for some whales.{{citation needed|date=October 2014}} Elephants also 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. These calls may be used to coordinate the movement of herds and allow [[mating elephants]] to find each other.<ref>{{Citation|last=Garstang|first=Michael|title=Chapter 3.2 - Elephant infrasounds: long-range communication|date=2010-01-01|url=http://www.sciencedirect.com/science/article/pii/S156973391070014X|work=Handbook of Behavioral Neuroscience|volume=19|pages=57–67|editor-last=Brudzynski|editor-first=Stefan M.|series=Handbook of Mammalian Vocalization|publisher=Elsevier|doi=10.1016/B978-0-12-374593-4.00007-3 |language=en|access-date=2020-01-27|url-access=subscription}}</ref>

:* Human singers: some vocalists, including [[Tim Storms]], can produce notes in the infrasound range.<ref>{{cite web |url=http://www.medicaldaily.com/man-worlds-deepest-voice-hits-notes-only-elephants-can-hear-242157 |title=Man With World's Deepest Voice Hits Notes That Only Elephants Can Hear |last1=Hsu |first1=Christine |date=24 August 2012 |website=Medical Daily |access-date=2 August 2016 |quote=American singer Tim Storms who also has the world's widest vocal range can reach notes as low as G-7 (0.189Hz) [...] so low that even Storms himself cannot hear it.}}</ref>

:* Man-Made sources: infrasound can be generated by human processes such as [[sonic boom]]s and [[explosion]]s (both chemical and [[nuclear explosion|nuclear]]), or by machinery such as [[diesel engine]]s, [[wind turbine]]s and specially designed mechanical [[transducers]] (industrial vibration tables). Certain specialized [[loudspeaker]] designs are also able to reproduce extremely low frequencies; these include large-scale [[rotary woofer]] models of [[subwoofer]] loudspeaker,<ref name="isbn0-8493-5091-3">{{cite book |editor-first=C.H.|editor-last=Chen|title=Signal and Image Processing for Remote Sensing |url=https://archive.org/details/signalimageproce00chen|url-access=limited|publisher=CRC |location=Boca Raton |year= 2007 |page= [https://archive.org/details/signalimageproce00chen/page/n50 33]|isbn=978-0-8493-5091-7}}</ref> as well as large [[Loudspeaker enclosure#Horn enclosures|horn loaded]], [[Loudspeaker enclosure#Ported (or reflex) enclosures|bass reflex]], [[Loudspeaker enclosure#Closed-box (sealed) enclosures|sealed]] and [[Loudspeaker enclosure#Transmission line|transmission line]] loudspeakers.<ref name="data_bass">{{Cite web | url=http://www.data-bass.com/systems | title=Data-Bass | website=Data-bass.com | access-date=12 May 2016 | archive-date=9 May 2016 | archive-url=https://web.archive.org/web/20160509225310/http://www.data-bass.com/systems | url-status=dead }}</ref><ref name="tdl_reference">{{Cite web | url=http://www.imf-electronics.com/Home/imf/speaker-range/reference-speakers | title=The Reference's&nbsp;— IMF electronics | website=Imf-elecctronics.com | access-date=27 October 2014 | archive-date=27 October 2014 | archive-url=https://web.archive.org/web/20141027080546/http://www.imf-electronics.com/Home/imf/speaker-range/reference-speakers | url-status=dead }}</ref>

== {{anchor|Animal reactions to infrasound}}Animal reaction ==
{{main|Perception of infrasound}}
{{Further|Tsunami#Possible animal reaction|Rayleigh wave#Possible animal reaction}}
Some animals have been thought to perceive the infrasonic waves going through the earth, caused by natural disasters, and to use these as an early warning. An example of this is the [[2004 Indian Ocean earthquake and tsunami]]. Animals were reported to have fled the area hours before the actual tsunami hit the shores of Asia.<ref>{{cite web |last1=Malone |first1=Elizabeth |last2=Deretsky |first2=Zina |title=After the tsunami |url=https://www.nsf.gov/news/special_reports/tsunami/index_low.jsp?id=preparing |url-status=dead |publisher=[[National Science Foundation]] |access-date=26 December 2011 |archive-url=https://web.archive.org/web/20171124170048/https://www.nsf.gov/news/special_reports/tsunami/index_low.jsp?id=preparing |archive-date=24 November 2017 }}</ref><ref>{{cite magazine |last=Kenneally |first=Christine |date=30 December 2004 |title=How did animals survive the tsunami? |url=https://slate.com/news-and-politics/2004/12/how-did-animals-survive-the-tsunami.html |magazine=Slate Magazine}}</ref> It is not known for sure that this is the cause; some have suggested that it may have been the influence of [[electromagnetic waves]], and not of infrasonic waves, that prompted these animals to flee.<ref>{{Cite web|url=https://www.pbs.org/wnet/nature/can-animals-predict-disaster-introduction-2/134/|title=Can Animals Predict Disaster? |date=5 June 2008|website=Pbs.org|access-date=12 March 2022}}</ref>

Research in 2013 by Jon Hagstrum of the US Geological Survey suggests that [[homing pigeons]] use low-frequency infrasound to navigate.<ref name="Knight">{{Cite journal|first=Kathryn|last=Knight|title=Disappearing Homing Pigeon Mystery Solved |date=15 February 2013|journal=Journal of Experimental Biology|volume=216|issue=4|pages=i|doi=10.1242/jeb.085506|s2cid=86492016 |doi-access=free}}</ref>

== {{anchor|Human reactions to infrasound}}Human reactions ==
{{Further|Health effects from noise}}

20&nbsp;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&nbsp;Hz.<ref>{{cite book |title=Music, Physics and Engineering |last=Olson |first=Harry F. |author-link=Harry F. Olson |year= 1967|publisher=Dover Publications |isbn=978-0-486-21769-7 |page=[https://archive.org/details/musicphysicsengi0000olso/page/249 249] |url=https://archive.org/details/musicphysicsengi0000olso |url-access=registration }}</ref> Below 10&nbsp;Hz it is possible to perceive the single cycles of the sound, along with a sensation of pressure at the eardrums.

From about 1000&nbsp;Hz, the dynamic range of the auditory system decreases with decreasing frequency. This compression is observable in the [[Equal-loudness contour|equal-loudness-level contours]], and it implies that even a slight increase in level can change the perceived loudness from barely audible to loud. Combined with the natural spread in [[Absolute threshold of hearing|thresholds]] within a population, its effect may be that a very low-frequency sound which is inaudible to some people may be loud to others.{{Citation needed|date=January 2024}}

One study has suggested that infrasound may cause feelings of awe or fear in humans. It has also been suggested that since it is not consciously perceived, it may make people feel vaguely that odd or [[supernatural]] events are taking place.<ref name="msnbc.com">{{cite web | title = Infrasound linked to spooky effects | url = https://www.nbcnews.com/id/wbna3077192 |publisher=NBC News  | date =7 September 2003  }}</ref>

A scientist working at Sydney University's Auditory Neuroscience Laboratory reports growing evidence that infrasound may affect some people's nervous system by stimulating the [[vestibular system]], and this has shown in animal models an effect similar to [[sea sickness]].<ref>{{cite web| title=Wind farm effect on balance 'akin to seasickness': scientist | url=http://www.theaustralian.com.au/news/health-science/wind-farm-effect-on-balance-akin-to-seasickness-scientist/story-e6frg8y6-1227393700133| date=12 June 2015 | last=King | first=Simon | publisher=News Corp Australia}}</ref>

In research conducted in 2006 focusing on the impact of sound emissions from wind turbines on the nearby population, perceived infrasound has been associated to effects such as annoyance or fatigue, depending on its intensity, with little evidence supporting physiological effects of infrasound below the human perception threshold.<ref>{{cite journal|last1=Rogers|first1=Anthony|last2=Manwell|first2=James|title=Wright|journal=Sally|date=2006|page=9|citeseerx=10.1.1.362.4894}}</ref> Later studies, however, have linked inaudible infrasound to effects such as fullness, pressure or tinnitus, and acknowledged the possibility that it could disturb sleep.<ref>{{cite journal|last1=Salt|first1=Alec N.|last2=Kaltenbach|first2=James A.|title=Infrasound From Wind Turbines Could Affect Humans|journal=Bulletin of Science, Technology & Society|date=19 July 2011|volume=31|issue=4|pages=296–302|doi=10.1177/0270467611412555|s2cid=110190618}}</ref> Other studies have also suggested associations between noise levels in turbines and self-reported sleep disturbances in the nearby population, while adding that the contribution of infrasound to this effect is still not fully understood.<ref>{{cite journal|last1=Abbasi|first1=Milad|last2=Monnazzam|first2=Mohammad Reza|last3=Zakerian|first3=SayedAbbolfazl|last4=Yousefzadeh|first4=Arsalan|title=Effect of Wind Turbine Noise on Workers' Sleep Disorder: A Case Study of Manjil Wind Farm in Northern Iran|journal=Fluctuation and Noise Letters|date=June 2015|volume=14|issue=2|pages=1550020|doi=10.1142/S0219477515500200|bibcode=2015FNL....1450020A}}</ref><ref>{{cite journal|last1=Bolin|first1=Karl|last2=Bluhm|first2=Gösta|last3=Eriksson|first3=Gabriella|last4=Nilsson|first4=Mats E|title=Infrasound and low frequency noise from wind turbines: exposure and health effects|journal=Environmental Research Letters|date=1 July 2011|volume=6|issue=3|pages=035103|doi=10.1088/1748-9326/6/3/035103|bibcode=2011ERL.....6c5103B|url=http://liu.diva-portal.org/smash/get/diva2:450514/FULLTEXT02|doi-access=free}}</ref>

In a study at [[Ibaraki University]] in Japan, researchers said EEG tests showed that the infrasound produced by [[wind turbine]]s was "considered to be an annoyance to the technicians who work close to a modern large-scale wind turbine".<ref>{{cite news | title=Wind-farm workers suffer poor sleep, international studies find |url=https://theaustralian.com.au/national-affairs/climate/windfarm-workers-suffer-poor-sleep-international-studies-find/news-story/f02dbb4fa8f4731338e665536c553fdc |newspaper=The Australian |url-access=subscription}}</ref><ref>{{cite journal |title=Effect of Wind Turbine Noise on Workers' Sleep Disorder: A Case Study of Manjil Wind Farm in Northern Iran |journal=Fluctuation and Noise Letters |volume=14 |issue=2 |pages=1550020 |doi=10.1142/S0219477515500200 |year=2015 |last1=Abbasi |first1=Milad |last2=Monnazzam |first2=Mohammad Reza |last3=Zakerian |first3=Sayedabbolfazl |last4=Yousefzadeh |first4=Arsalan |bibcode=2015FNL....1450020A }}</ref><ref>{{cite journal|title=Analysis of aerodynamic sound noise generated by a large-scaled wind turbine and its physiological evaluation|journal=International Journal of Environmental Science and Technology|volume=12|issue=6|pages=1933–1944|date=10 April 2014|doi=10.1007/s13762-014-0581-4|last1=Inagaki|first1=T.|last2=Li|first2=Y.|last3=Nishi|first3=Y.|s2cid=56410935|url=http://www.bioline.org.br/abstract?id=st15180}}</ref>

Jürgen Altmann of the [[Technical University of Dortmund]], an expert on [[sonic weapon]]s, has said that there is no reliable evidence for nausea and vomiting caused by infrasound.<ref>[https://www.newscientist.com/article.ns?id=dn1564 ''The Pentagon considers ear-blasting anti-hijack gun'']&nbsp;— [[New Scientist]]</ref>

High volume levels at concerts from subwoofer arrays have been cited as causing [[lung collapse]] in individuals who are very close to the subwoofers, especially for smokers who are particularly tall and thin.<ref>{{Cite magazine|date=2 September 2004|url=https://www.wired.com/2004/09/music-fans-beware-the-big-bass/|title=Music Fans, Beware the Big Bass|access-date=12 March 2022|magazine=Wired}}</ref>

In September 2009, London student Tom Reid died in a club of [[sudden arrhythmic death syndrome]] (SADS) after complaining that "loud bass notes" from the club's speakers were "getting to his heart". The inquest recorded a verdict of natural causes, although some experts commented that the bass could have acted as a trigger.<ref>{{Cite news|url=https://metro.co.uk/2009/12/09/loud-bass-music-killed-student-tom-reid-622944/|title=Loud bass music 'killed student' Tom Reid|newspaper=[[Metro (British newspaper)|Metro]]|date=9 December 2009|access-date=12 March 2022}}</ref>

Air is a very inefficient medium for transferring low frequency vibration from a transducer to the human body.<ref>{{Cite journal|url=https://ui.adsabs.harvard.edu/abs/1977JSV....53..605R|title=Book Review: Infrasound and low frequency vibration. 1977, W. Tempest. London: Academic Press Inc. (London) Ltd.|first=G.|last=Rood|date=1 August 1977|journal=Journal of Sound and Vibration|volume=53|issue=4 |pages=605–606|access-date=12 March 2022|doi=10.1016/0022-460X(77)90533-8|bibcode=1977JSV....53..605R }}</ref> Mechanical connection of the vibration source to the human body, however, provides a potentially dangerous combination. The U.S. space program, worried about the harmful effects of rocket flight on astronauts, ordered vibration tests that used cockpit seats mounted on vibration tables to transfer "brown note" and other frequencies directly to the human subjects. Very high power levels of 160&nbsp;dB were achieved at frequencies of 2–3&nbsp;Hz. Test frequencies ranged from 0.5&nbsp;Hz to 40&nbsp;Hz. Test subjects suffered motor ataxia, nausea, visual disturbance, degraded task performance and difficulties in communication. These tests are assumed by researchers to be the nucleus of the current [[urban legend|urban myth]] surrounding the "brown note" and its effects.<ref>[https://web.archive.org/web/20071231012618/http://srforums.prosoundweb.com/index.php/mv/tree/27986/261708/72/ ProSoundWeb: ''some effects of low end''] (bulletin board entry by [[Tom Danley]])</ref><ref>{{Cite web |url=http://www.danleysoundlabs.com/matterhorn.htm |title=Matterhorn |date=13 January 2008 |website= |access-date=12 March 2022 |archive-url=https://web.archive.org/web/20080113051923/http://www.danleysoundlabs.com/matterhorn.htm |archive-date=13 January 2008 |url-status=dead}}</ref>{{Clarify|reason=what urban myth?|date=May 2023}}

The report "A Review of Published Research on Low Frequency Noise and its Effects"<ref>{{cite web |url=http://www.defra.gov.uk/environment/noise/research/lowfrequency/pdf/lowfreqnoise.pdf |title=A Review of Published Research on Low Frequency Noise and its Effects |website=Defra.gov.uk |access-date=11 January 2022 |archive-url=https://web.archive.org/web/20080920193328/http://www.defra.gov.uk/environment/noise/research/lowfrequency/pdf/lowfreqnoise.pdf |archive-date=20 September 2008 |url-status=dead}}</ref> contains a long list of research about exposure to high-level infrasound among humans and animals.  For instance, in 1972, Borredon exposed 42 young men to tones at 7.5&nbsp;Hz at 130&nbsp;dB for 50 minutes. This exposure caused no adverse effects other than reported drowsiness and a slight blood pressure increase.  In 1975, Slarve and Johnson exposed four male subjects to infrasound at frequencies from 1 to 20&nbsp;Hz, for eight minutes at a time, at levels up to 144&nbsp;dB SPL.  There was no evidence of any detrimental effect other than middle ear discomfort. Tests of high-intensity infrasound on animals resulted in measurable changes, such as cell changes and ruptured blood vessel walls.

Infrasound is one hypothesized cause of death for the nine Soviet hikers who were [[Dyatlov Pass incident|found dead at Dyatlov Pass]] in 1959.<ref>{{cite web |url=http://failuremag.com/article/return-to-dead-mountain |title=Return to Dead Mountain;— Kármán vortex street, infrasound at Dyatlov Pass |date=2014-02-01 |website=failuremag.com |language=en |archive-url=https://web.archive.org/web/20220122232405/http://failuremag.com/article/return-to-dead-mountain |archive-date=22 January 2022 |url-status=dead}}</ref>

=== Hygienic standards in the workplace ===
'''US:''' Maximum levels for frequencies from 1 to 80 Hz are no more than 145 dB. Overall level (for all frequencies) - no more than 150 dB.<ref>{{cite book |title=2020 TLVs and BEIs Book |date=2020 |publisher=American Conference of Governmental Industrial Hygienists |location=Cincinnati, Ohio |isbn=978-1-607261-12-4 |pages=126–127 |chapter=Acoustic — Infrasound and Low-Frequency Sound}}</ref>

{| class="wikitable collapsible collapsed" style="text-align:center"
|+ RF<ref name="СанПиН">{{cite book |title=State hygienic requirements 1.2.3685-21 "Hygienic requirements for the safety of environmental factors for humans" [СанПиН 1.2.3685-21 "Гигиенические нормативы и требования к обеспечению безопасности и (или) безвредности для человека факторов среды обитания"] |date=2021 |publisher=[[Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing]] |location=Moscow |page=338 |url=http://publication.pravo.gov.ru/Document/View/0001202102030022 |access-date=4 July 2024 |language=ru |chapter=§ 35, Table 5.5}}</ref>
|-
! colspan="4" | Equivalent sound pressure levels, dB, in octave bands with geometric mean frequencies, Hz 
! rowspan="2" | Equivalent overall sound pressure level, dB
! rowspan="2" | Maximum overall infrasound level, dB
|-
| 2 || 4 || 8 || 16
|-
| 100 || 95 || 90 || 85 || 100 || 120
|}

=== Brown note ===
{{Main|Brown note}}

The brown note is a hypothetical infrasonic frequency capable of causing fecal incontinence by creating acoustic resonance in the human bowel. Attempts to demonstrate the existence of a "brown note" using sound waves transmitted through the air have failed.

In February 2005 the television show ''[[MythBusters]]'' attempted to verify whether the "brown note" was a reality. They tested notes down to 5&nbsp;Hz in frequency and up to 153&nbsp;dB in [[sound pressure]]. They used a type  subwoofer used for major rock concerts, and which had been specially modified for deeper bass extension. The rumored physiological effects did not materialize. The show declared the brown note myth "busted."<ref>{{cite web|url=http://www.discovery.com/tv-shows/mythbusters/mythbusters-database/brown-note/ |title=Brown Note &#124; MythBusters |publisher=Discovery |date=2012-04-11 |access-date=2016-05-29}}</ref><ref>{{cite web| url=http://www.meyersound.com.au/brownnote.shtm| title=Brown Note| publisher=Meyer Sound| year=2000| access-date=2006-08-30| url-status=dead| archive-url=https://web.archive.org/web/20060906094120/http://www.meyersound.com.au/brownnote.shtm| archive-date=2006-09-06}}</ref><ref>{{Cite web |url=http://www.meyersound.com/pdf/products/concert_series/700-hp_ds.pdf |title=Meyer Sound 700-HP UltraHigh-Power Subwoofer datasheet |access-date=2007-11-14 |archive-url=https://web.archive.org/web/20071021075207/http://www.meyersound.com/pdf/products/concert_series/700-hp_ds.pdf |archive-date=2007-10-21 |url-status=dead }}</ref><ref name=Meyer2004>{{cite web|url=http://meyersound.com/news/2004/brown_note/index.php|title=Meyer Sound Gets Down to Basics in MythBusters Episode|date=September 2004|publisher=Meyer Sound Laboratories|access-date=1 September 2010|archive-url=https://web.archive.org/web/20110714081338/http://meyersound.com/news/2004/brown_note/index.php|archive-date=2011-07-14|url-status=dead}}</ref>

=== ''Infrasonic'' 17&nbsp;Hz tone experiment ===
On 31 May 2003, a group of UK researchers held a mass experiment, where they exposed some 700 people to music laced with soft 17&nbsp;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 Room]] over the course of two performances, each consisting of four musical pieces. Two of the pieces in each concert had 17&nbsp;Hz tones played underneath.<ref name="Infrasonic">[https://web.archive.org/web/20131001154912/http://www.spacedog.biz/Infrasonic/sounds/infrasonic ''Infrasonic''] concert, Purcell Room, London, 31 May 2003, sponsored by the ''sciart Consortium'' with additional support by the [[National Physical Laboratory, UK|National Physical Laboratory (NPL)]]</ref><ref name="smh.com.au">{{Cite news|url=https://www.smh.com.au/national/sounds-like-terror-in-the-air-20030909-gdhcu4.html|title=Sounds like terror in the air|date=9 September 2003|newspaper=[[The Sydney Morning Herald]]|access-date=12 March 2022}}</ref>

In the second concert, the pieces that were to carry a 17&nbsp;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&nbsp;Hz near-infrasonic tone. The presence of the tone resulted in a significant number (22%) of respondents reporting feeling uneasy or sorrowful, getting chills down the spine or nervous feelings of revulsion or fear.<ref name="Infrasonic" /><ref name="smh.com.au" />

In presenting the evidence to the [[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 [[List of reportedly haunted locations|allegedly haunted sites]] and so cause people to have [[Apparitional experience|odd sensations]] that they attribute to a ghost—our findings support these ideas."<ref name="msnbc.com" />

=== Suggested relationship to ghost sightings ===
[[Psychologist]] [[Richard Wiseman]] of the [[University of Hertfordshire]] suggests that the odd sensations that people attribute to ghosts may be caused by infrasonic vibrations. [[Vic Tandy]], experimental officer and part-time lecturer in the school of international studies and law at [[Coventry University]], along with Dr. Tony Lawrence of the University's psychology department, wrote in 1998 a paper called "Ghosts in the Machine" for the ''Journal of the [[Society for Psychical Research]]''. Their research suggested that an infrasonic signal of 19&nbsp;Hz might be responsible for [[Apparitional experience|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 (fencing)|foil]], with the handle held in a [[Vice (tool)|vice]]. 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&nbsp;Hz, very close to the [[resonant frequency]] of the eye given as 18&nbsp;Hz by NASA.<ref>[https://apps.dtic.mil/sti/pdfs/ADA030476.pdf NASA Technical Report 19770013810], Dtic.mil</ref> This, Tandy conjectured, was why he had seen a ghostly figure—it was, he believed, 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.<ref>{{Cite web|url=http://skepdic.com/infrasound.html|title=infrasound&nbsp;— The Skeptic's Dictionary|website=Skepdic.com|access-date=12 March 2022}}</ref>

Tandy investigated this phenomenon further and wrote a paper entitled ''The Ghost in the Machine''.<ref>{{Cite journal  | last1 = Tandy | first1 = V. | last2 = Lawrence | first2 = T. | title = The ghost in the machine. | journal = [[Journal of the Society for Psychical Research]] | volume = 62 | issue = 851 | pages = 360–364 |date=April 1998 | url = http://www.richardwiseman.com/resources/ghost-in-machine.pdf }}</ref> 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]]<ref>{{Cite journal  | last1 = Tandy | first1 = V. | title = Something in the cellar. | journal = Journal of the Society for Psychical Research | volume = 64.3 | issue = 860 |date=July 2000 | url = http://www.psy.herts.ac.uk/ghost/Something-in-the-Cellar.pdf | archive-url = https://web.archive.org/web/20110929142806/http://www.psy.herts.ac.uk/ghost/Something-in-the-Cellar.pdf |archive-date = 2011-09-29}}</ref><ref>{{cite news| url=https://www.theguardian.com/education/2000/jul/11/highereducation.chrisarnot |work=The Guardian  | location=London | title=Ghost buster | first=Chris | last=Arnot | date=11 July 2000 }}</ref> and [[Edinburgh Castle]].<ref>[http://www.coventrytelegraph.net/news/coventry-news/page.cfm?objectid=12722447&method=full&siteid=50003 Who ya gonna call? Vic Tandy!]&nbsp;– [[Coventry Telegraph]] {{webarchive |url=https://web.archive.org/web/20110501124446/http://www.coventrytelegraph.net/news/coventry-news/page.cfm?objectid=12722447&method=full&siteid=50003 |date=1 May 2011 }}</ref><ref>{{Cite web |url=http://www.ghostexperiment.co.uk/theories-infra.html |title=The Ghost Experiment&nbsp;— theories, infrasound |date=19 January 2007 |website= |access-date=12 March 2022 |archive-url=https://web.archive.org/web/20070119004339/http://www.ghostexperiment.co.uk/theories-infra.html |archive-date=19 January 2007 |url-status=dead}}</ref>

== Detection and measurement ==
{{see also|Infrasonic sensing array}}
[[NASA Langley]] has designed and developed an infrasonic detection system that can be used to make useful infrasound measurements at a location where it was not possible previously. The system comprises an [[Electret microphone|electret condenser microphone]] PCB Model 377M06, having a 3-inch membrane diameter, and a small, compact windscreen.<ref name=WakeVortex>[http://www.wakenet.eu/fileadmin/user_upload/Workshop2014/Presentations/WakeNetEurope_Workshop2014_401_Shams.pdf Development and installation of an infrasonic wake vortex detection system] By Qamar A. Shams and Allan J. Zuckerwar, NASA Langley Research Center, Hampton VA USA, WakeNet-Europe 2014, Bretigny, France.</ref> Electret-based technology offers the lowest possible background noise, because [[Johnson noise]] generated in the supporting electronics (preamplifier) is minimized.<ref name=WakeVortex />

The microphone features a high membrane compliance with a large backchamber volume, a prepolarized backplane and a high impedance preamplifier located inside the backchamber. The windscreen, based on the high transmission coefficient of infrasound through matter, is made of a material having a low acoustic impedance and has a sufficiently thick wall to ensure structural stability.<ref name=NASALangley>{{cite web |last=Atkinson |first=Joe |date=25 July 2014 |title=NASA Langley Researchers Nab Invention of the Year for Infrasound Detection System |url=http://www.nasa.gov/larc/nasa-langley-researchers-nab-invention-of-the-year-for-infrasound-detection-system/ |publisher=NASA Langley Research Center |url-status=dead |archive-url=https://web.archive.org/web/20141027131146/https://www.nasa.gov/larc/nasa-langley-researchers-nab-invention-of-the-year-for-infrasound-detection-system/ |archive-date=27 October 2014}}</ref> Close-cell polyurethane foam has been found to serve the purpose well. In the proposed test, test parameters will be sensitivity, background noise, signal fidelity (harmonic distortion), and temporal stability.

The microphone design differs from that of a conventional audio system in that the peculiar features of infrasound are taken into account. First, infrasound propagates over vast distances through the Earth's atmosphere as a result of very low atmospheric absorption and of refractive ducting that enables propagation by way of multiple bounces between the Earth's surface and the stratosphere. A second property that has received little attention is the great penetration capability of infrasound through solid matter&nbsp;– a property utilized in the design and fabrication of the system windscreens.<ref name=NASALangley />

Thus the system fulfills several instrumentation requirements advantageous to the application of acoustics: (1) a low-frequency microphone with especially low background noise, which enables detection of low-level signals within a low-frequency passband; (2) a small, compact windscreen that permits (3) rapid deployment of a microphone array in the field. The system also features a data acquisition system that permits real time detection, bearing, and signature of a low-frequency source.<ref name=NASALangley />

=== Infrasound for nuclear detonation detection ===
Infrasound is one of several techniques used to identify if a nuclear detonation has occurred. A network of 60 infrasound stations, in addition to seismic and hydroacoustic stations, comprise the [[International Monitoring System]] (IMS) that is tasked with monitoring compliance with the [[Comprehensive Nuclear-Test-Ban Treaty|Comprehensive Nuclear Test-Ban Treaty]] (CTBT).<ref name=":6">{{Cite web|date=30 March 2020|url=http://can-ndc.nrcan.gc.ca/is_infrasound-en.php|title=IMS Infrasound Network|publisher=Natural Resources Canada|website=can-ndc.nrcan.gc.ca|language=en|access-date=2017-04-25}}</ref> IMS Infrasound stations consist of eight [[microbarometer]] sensors and space filters arranged in an array covering an area of approximately 1 to 9&nbsp;km<sup>2</sup>.<ref name=":6" /><ref name=":7">{{Cite web|url=http://www.ga.gov.au/scientific-topics/hazards/nuclear-monitoring/techniques/infrasound|title=Infrasound Monitoring|date=2014-05-15|website=Ga.gov.au|language=EN|access-date=2017-04-25}}</ref> The space filters used are radiating pipes with inlet ports along their length, designed to average out pressure variations like wind turbulence for more precise measurements.<ref name=":7" /> The microbarometers used are designed to monitor frequencies below approximately 20 hertz.<ref name=":6" /> Sound waves below 20 hertz have longer wavelengths and are not easily absorbed, allowing for detection across large distances.<ref name=":6" />

Infrasound wavelengths can be generated artificially through detonations and other human activity, or naturally from earthquakes, severe weather, lightning, and other sources.<ref name=":6" /> Like [[forensic seismology]], algorithms and other filter techniques are required to analyze gathered data and characterize events to determine if a nuclear detonation has actually occurred. Data is transmitted from each station via secure communication links for further analysis. A digital signature is also embedded in the data sent from each station to verify if the data is authentic.<ref>{{Cite web|url=https://www.ctbto.org/verification-regime/monitoring-technologies-how-they-work/infrasound-monitoring/|title=Infrasound monitoring |publisher=CTBTO Preparatory Commission|website=Ctbto.org|language=en|access-date=2017-04-25|url-status=deviated|archive-url=https://web.archive.org/web/20170203034207/https://www.ctbto.org/verification-regime/monitoring-technologies-how-they-work/infrasound-monitoring/|archive-date=3 February 2017}}</ref>

The [[comprehensive Test Ban Treaty|Comprehensive Nuclear-Test-Ban Treaty Organization Preparatory Commission]] uses infrasound as one of its monitoring technologies, along with [[seismology|seismic]], [[hydrophone|hydroacoustic]], and [[radionuclide|atmospheric radionuclide]] monitoring. The loudest infrasound recorded to date by the monitoring system was generated by the 2013 [[Chelyabinsk meteor]].<ref name="mel">{{Cite news |url=http://www.nzherald.co.nz/world/news/article.cfm?c_id=2&objectid=10866592 |title=Meteor explosion largest infrasound recorded |last=Harper |first=Paul |access-date=31 March 2013 |date=20 February 2013 |newspaper=The New Zealand Herald |publisher=APN Holdings NZ }}</ref>

== In popular culture ==
The 2017 film ''[[The Sound (film)|The Sound]]'' uses infrasound as a major plot element.<ref>{{Cite web|last=Lowe|first=Justin|date=3 October 2017|title='The Sound': Film Review|url=https://www.hollywoodreporter.com/review/sound-1044371|access-date=29 March 2021|website=The Hollywood Reporter|quote=Continuing her search, Kelly soon encounters ghostly apparitions and overwhelming low-frequency sound waves below the threshold of human hearing that emanate from a source she’s unable to identify with her audio gear.}}</ref><ref>{{Cite web|last=Kermode|first=Jennie|date=27 September 2017|title=The Sound (2017) Movie Review from Eye for Film|url=https://www.eyeforfilm.co.uk/review/the-sound-2017-film-review-by-jennie-kermode|access-date=29 March 2021|website=Eye For Film}}</ref>

In "Fermata", a 2020 episode of the Franco-Belgian TV series ''[[Astrid et Raphaëlle]]'', infrasound from a generator hidden in the pipe organ of the [[Grand Auditorium (Maison de la Radio)|Grand Auditorium]] in the [[Maison de la Radio et de la Musique]], the Paris headquarters of [[Radio France]], is used as a murder weapon.

The 'ghost frequency' phenomenon is mentioned in Season 3 Episode 4 of the TV Series [[Evil (TV series)|Evil]], ''The Demon of the Road.''

== See also ==
{{div col|colwidth=22em}}
* [[Bioacoustics]]
* [[Blaster beam]]
* [[Brown note]]
* [[Clear-air turbulence]]
* [[Contrabass tuba]]
* [[Feraliminal Lycanthropizer]]
* [[Havana syndrome]]
* [[Helmholtz resonance]]
* [[The Hum]]
* [[Low-frequency oscillation]]
* [[Microbarom]]
* [[Sonic weapon]]
* [[Subcontrabass tuba]]
* [[Ultrasound]]
{{div col end}}

== References ==
;Notes
{{Reflist}}

;Bibliography
* Gundersen, P. Erik. ''The Handy Physics Answer Book''. Visible Ink Press, 2003.
* Chedd, Graham. ''Sound; From Communications to Noise Pollution''. [[Doubleday & Company]], 1970.
* O'Keefe, Ciaran, and Sarah Angliss. [https://web.archive.org/web/20131225083806/http://www.uni-graz.at/richard.parncutt/cim04/proceedings_.htm The Subjective Effects of Infrasound in a Live Concert Setting]. [https://web.archive.org/web/20131225084105/http://www.uni-graz.at/richard.parncutt/cim04/welcome.htm ''CIM04: Conference on Interdisciplinary Musicology'']. [[Graz]], Austria: Graz UP, 2004. 132–133.
* ''Discovery's Biggest Shows aired'' at 8:00&nbsp;pm (Indian Standard Time) on [[The Discovery Channel]], India on Sunday, 7 October 2007

== External links ==
{{Wiktionary}}
* [https://web.archive.org/web/20200408192005/https://psl.noaa.gov/programs/infrasound/ NOAA Infrasonics Program (archived)]
* [https://web.archive.org/web/20070904211118/http://www.rdss.info/index_ns.html US Army Space and Missile Defense Command Monitoring Research Program (archived)]
* [https://web.archive.org/web/20041024230907/http://www.ees.lanl.gov/Resources/infra_collab.shtml Los Alamos Infrasound Monitoring Laboratory (archived)]
* [https://pubs.usgs.gov/pinatubo/tahira/index.html Infrasonic and Acoustic-Gravity Waves Generated by the Mount Pinatubo Eruption of 15 June 1991], Makoto Tahira, Masahiro Nomura, Yosihiro Sawada and Kosuke Kamo
* [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090009968.pdf Sub-surface windscreen for the measurement of outdoor infrasound] Qamar A. Shams, Cecil G. Burkett and Toby Comeaux NASA Langley Research Center, Allan J. Zuckerwar Analytical Services and Material, and George R. Weistroffer Virginia Commonwealth University

{{Acoustics}}
{{Authority control}}

[[Category:Sound]]