Search results
Results from the WOW.Com Content Network
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.
[9] [10] During emission of 22-kHz calls, juveniles and adults are often exhibiting freezing behaviour and experiencing an increase in heart rate and blood pressure. [1] Since 22-kHz calls are emitted in response to unpleasant situations and noxious stimuli, it has been thought that these calls serve two functions: reflecting anxiety, and ...
Printable version; Page information; ... United States Frequency Allocations Chart 2011 ... Version of PDF format: 1.4
For frequencies of ultrasound from 25 to 50 kHz, a guideline of 110 dB had been recommended by Canada, Japan, the USSR, and the International Radiation Protection Agency, and 115 dB by Sweden [24] in the late 1970s to early 1980s, but these were primarily based on subjective effects. The more recent OSHA guidelines above are based on ACGIH ...
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 attenuation is frequency-dependent: higher frequencies are attenuated faster with increasing depth. Selecting ultrasound detectors that are most sensitive at the appropriate frequency can improve sensitivity at the target imaging depth, but at the cost of spatial resolution.
Medical ultrasound includes diagnostic techniques (mainly imaging techniques) using ultrasound, as well as therapeutic applications of ultrasound. In diagnosis, it is used to create an image of internal body structures such as tendons, muscles, joints, blood vessels, and internal organs, to measure some characteristics (e.g., distances and velocities) or to generate an informative audible sound.
Ultrasound energy, simply known as ultrasound, is a type of mechanical energy called sound characterized by vibrating or moving particles within a medium. Ultrasound is distinguished by vibrations with a frequency greater than 20,000 Hz, compared to audible sounds that humans typically hear with frequencies between 20 and 20,000 Hz.