Which of the following ranges belong to the ultrasound frequency?

below 20Hz above 20Hz below 20kHz above 20kHz

above 20kHz

Ultrasound is an oscillating sound pressure wave with a frequency greater than the upper limit of the human hearing range. Ultrasound is thus not separated from normal (audible) sound by differences in physical properties, only by the fact that humans cannot hear it. Although this limit varies from person to person, it is approximately 20,000 hertz in healthy, young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz. Hence, Ultrasound is of frequency 20,000 Hz and above.