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| Some ] soundtracks also make use of infrasound to produce unease or disorientation in the audience. '']'' is one such movie. | Some ] soundtracks also make use of infrasound to produce unease or disorientation in the audience. '']'' is one such movie. | ||
| ==See also== | |||
| * ] (sound at extremely high frequencies) | |||
| * ] (a frequency of sound purported to be the "]" - a specific infrasonic frequency rumored to cause lack of bowel control) | |||
| == References == | |||
| * ''infrasound''. Collins English Dictionary (2000). Retrieved 25 October 2005, from xreferplus. http://www.xreferplus.com/entry/2657949 | |||
| ==External links== | |||
| * - from About.com | |||
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| *, Makoto Tahira, Masahiro Nomura, Yosihiro Sawada and Kosuke Kamo | |||
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Revision as of 04:23, 1 November 2005
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.
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).
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 that migrating birds use naturally generated infrasound, from sources such as turbulent airflow over mountain ranges, as a navigational aid.
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 British Association, 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".
Some film soundtracks also make use of infrasound to produce unease or disorientation in the audience. Irréversible is one such movie.