Ultrasound Scannerissound waveswithfrequencieshigher than the upper audible limit of humanhearing.Ultrasound Scanneris no different from ‘normal’ (audible) sound in its physical properties, except in that humans cannot hear it. This limit varies from person to person and is approximately 20kilohertz(20,000 hertz) in healthy young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz.

Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and measure distances.Ultrasound imagingor sonography is often used inmedicine. In thenondestructive testingof products and structures,Ultrasound Scanneris used to detect invisible flaws. Industrially, ultrasound is used for cleaning, mixing, and to accelerate chemical processes. Animals such asbatsandporpoisesuse ultrasound for locating猎物and obstacles.^[1]Scientist are also studying ultrasound usinggraphenediaphragmsas a method of communication.

Humans

The upper frequency limit in humans (approximately 20 kHz) is due to limitations of themiddle ear.Auditory sensationcan occur if high‐intensity ultrasound is fed directly into thehuman skulland reaches thecochleathroughbone conduction, without passing through the middle ear.^[4]

Children can hear some high-pitched sounds that older adults cannot hear, because in humans the upper limit pitch of hearing tends to decrease with age.^[5]An Americancell phonecompany has used this to create ring signals supposedly only able to be heard by younger humans;^[6]but many older people can hear the signals, which may be because of the considerable variation of age-related deterioration in the upper hearing threshold.The Mosquitois an electronic device that uses a high pitched frequency to deterloiteringby young people.