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Ultra low frequency (ULF) is the ITU designation [1] [2] for the frequency range of electromagnetic waves between 300 hertz and 3 kilohertz, corresponding to wavelengths between 1,000 to 100 km. In magnetosphere science and seismology , alternative definitions are usually given, including ranges from 1 mHz to 100 Hz, [ 3 ] 1 mHz to 1 Hz, [ 4 ...
Infrasound arrays at monitoring station in Qaanaaq, Greenland.. Infrasound, sometimes referred to as low frequency sound or subsonic, 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). [1]
Bloop is the name given to an ultra-low-frequency and extremely powerful underwater sound detected by the U.S. National Oceanic and Atmospheric Administration (NOAA) in 1997. The sound is consistent with the noises generated by icequakes in large icebergs, or large icebergs scraping the ocean floor. [3]
Bloop was an ultra-low-frequency, ... the sound "rose" in frequency over about one minute and was of sufficient amplitude to be heard on multiple sensors, at a range ...
Since the early 1960s, researchers have been experimenting with creating directive low-frequency sound from nonlinear interaction of an aimed beam of ultrasound waves produced by a parametric array using heterodyning. Ultrasound has much shorter wavelengths than audible sound, so that it propagates in a much narrower beam than any normal ...
Extremely low frequency (ELF) is the ITU designation [1] for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. [2] [3] In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz.
The symptoms resembled those of individuals who had suffered minor head injuries. One theory for a causal mechanism is that the prolonged sound exposure resulted in enough mechanical strain to brain tissue to induce an encephalopathy. Divers and aquatic mammals may also suffer lung and sinus injuries from high intensity, low-frequency sound.
Seismic exploration involves the use of low frequency sound (< 100 Hz) to probe deep into the seabed. Despite the relatively poor resolution due to their long wavelength, low frequency sounds are preferred because high frequencies are heavily attenuated when they travel through the seabed. Sound sources used include airguns, vibroseis and ...