Themes > Science > Physics > Acoustics > General Properties of Sound > Ultrasound


Frequencies generally are divided into infrasound, audible sound and ultrasound.  Audible  frequency sounds are those that we can hear, generally restricted to sound frequencies in the 20 Hz to 20 kHz range. 

Classification of Sounds According to Frequency
Above 20,000 Hz (20 kHz) Ultrasound
20 Hz to 20,000 Hz (20 kHz) Audible Sound
Below 20 Hz "Infra-sound"

Ultrasound refers to any sound whose frequency is above the audible range, ie, above 20 kHz.  Diagnostic ultrasound frequencies usually are at least 1 MHz. Keep in mind, however, that the definition of ultrasound includes a wider range of frequencies than simply those used in medical ultrasound.


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