Frequency of Sound In Ultrasound.

 The frequency (j) is the number of times the wave oscillates through a cycle each second (sec). Sound waves with frequencies less than 15 cycles/sec (Hz) are called infrasound, and the range between 15 Hz and 20 kHz comprises the audible acoustic spectrum. Ultrasound represents the frequency range above 20 kHz.

Medical ultrasound uses frequencies in the range of 2 to 10 MHz, with specialized ultrasound applications up to 50 MHz. The period is the time duration of one wave cycle, and is equal to 1/f, where fis expressed in cycles/sec.

                The ultrasound frequency is unaffected by changes in sound speed as the acoustic beam propagates through various media. Thus, the ultrasound wavelength is dependent on the medium.