What Is Ultrasound?
Ultrasound is a very high-pitched sound. Within sound there are different frequencies. The human ear can detect sound with frequencies between 20 Hz and 20,000 Hz. Ultrasound is like the ordinary sound we hear except that is has a higher frequency then that to which the human hearing system responds.
The frequency of sound is measured in Hertz (Hz) or Megahertz (MHz). Hertz relates to one cycle of sound per second. Megahertz relates to one million, therefore, one Megahertz is 1,000,000 Hz. For example, in music, middle C has a frequency of about 500 Hz. Some animals like dolphins and bats can send out sound as well as receive sound at frequencies above 20 kHz.
Ultrasound produces sound through mechanical vibrations at above 20,000 Hz, any sound at this level or above this is defined as Ultrasound. The Ultrasound used in medical imaging is between 3 to 15 MHz.
