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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"), [1] describes sound waves with a frequency below the lower limit of human audibility (generally 20 Hz, as defined by the ANSI/ASA S1.1-2013 standard). [2]
For army infrasound applications, the target frequency range was in the 1–20 Hz band. [3] Infrasound has the ability to reach distances of 100–500 km. There are natural sources of infrasound emissions, such as avalanches, tornados, volcanoes, earthquakes and man-made sources of infrasound, such as aircraft engines, helicopters, artillery ...
Infrasound works by having multiple stations that use microbarometers to listen for infrasonic waves caused by explosions, volcanoes or other natural occurring events. [10] As with other detection methods, infrasound was developed during the Cold War. [11] These stations were designed to detect explosions with forces as low as 1 kiloton.
The UK's independent Advisory Group on Non-ionising Radiation (AGNIR) produced a 180-page report on the health effects of human exposure to ultrasound and infrasound in 2010. The UK Health Protection Agency (HPA) published their report, which recommended an exposure limit for the general public to airborne ultrasound sound pressure levels (SPL ...
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Infrasound sensitive fibers are found to be simple bipolar cells in the auditory ganglion with a diameter of 1.6-2.2 μm at the axon and 0.9-1.2 μm at the dendrites. [19] They originate in the apical end of the cochlea and they are located near fibers that transmit low frequency sounds in the acoustic range.
Recording microbarometers, or microbarographs, distributed around the world are planned to be used to monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty (upon entry into force) by detecting the infrasound signature of a nuclear explosion, which can propagate for very long distances. By analyzing the data received at several of ...
Microbaroms are a significant noise source that can potentially interfere with the detection of infrasound from nuclear explosions. Accurate detection of explosions is a goal of the International Monitoring System organized under the Comprehensive Nuclear-Test-Ban Treaty (which has not entered into force). [ 33 ]