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Ultrasonic hearing is a recognised auditory effect which allows humans to perceive sounds of a much higher frequency than would ordinarily be audible using the inner ear, usually by stimulation of the base of the cochlea through bone conduction. Normal human hearing is recognised as having an upper bound of 15–28 kHz, [1] depending on the person.
Ultrasound is sound with frequencies greater than 20 kilohertz. [1] This frequency is the approximate upper audible limit of human hearing in healthy young adults. The physical principles of acoustic waves apply to any frequency range, including ultrasound. Ultrasonic devices operate with frequencies from 20 kHz up to several gigahertz.
It is known, however, that humans can perceive sounds below this frequency at very high pressure levels. [1] Infrasound can come from many natural as well as man-made sources, including weather patterns, topographic features, ocean wave activity, thunderstorms, geomagnetic storms , earthquakes, jet streams , mountain ranges, and rocket launchings.
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.
Numerous other studies have contradicted the portion of the results relating to the subjective reaction to high-frequency audio, finding that people who have "good ears" [8] listening to Super Audio CDs and high resolution DVD-Audio recordings [9] on high fidelity systems capable of reproducing sounds up to 30 kHz [10] cannot tell the ...
The foods you eat play an important role in helping you lose visceral fat. Even those traditionally considered to be “bad”—like full-fat dairy, fruit and popcorn—can aid in fat loss.
The ultrasound has wavelengths only a few millimeters long which are much smaller than the source, and therefore naturally travel in an extremely narrow beam. The ultrasound, which contains frequencies far outside the range of human hearing, is completely inaudible.
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