Ultrasonic refers to sound that is beyond the audible hearing range; typically above 20 kHz (20,000 Hz). In medicine, ultrasound machines emit ultrasonic waves that echo back an image of a fetus or internal organ. They are also used to administer therapy to various parts of the body. Contrast with infrasonic
. See ultrasonic welding
Kardia Ultrasonic EKG Data Transfer
By placing fingers on this pad for 30 seconds, the body's electrical heart rhythm is converted to ultrasonic waves picked up by the Kardia app running in a smartphone nearby. The finger pad has no battery.