Ultrasoundsound with a frequency greater than the upper limit of
human hearing, approximately 20 kilohertz. Some animals, such as
dogs, dolphins, and bats, have an upper limit that is greater
than that of the human ear and thus can hear ultrasound.
Ultrasound has industrial and medical applications. Medical
ultrasonography can visualise muscle and soft tissue, making
them useful for scanning the organs. Typical diagnostic
ultrasound scanners operate in the frequency range of 2 to 10
megahertz. Powerful ultrasound may also be used to break up
kidney stones. Ultrasonic cleaners, sometimes called supersonic
cleaners, are used at frequencies from 20-40 kHz for jewellery,
lenses and other optical parts, watches, dental instruments,
surgical instruments and industrial parts. Home cleaners are
available and costs range from approximately US $100.