Ultrasounds are mechanical sound waves. A difference of acoustic phenomena properly said, the frequencies that characterize ultrasound are superior to those averagely audible to a human ear. The frequency conventionally used to discriminate the sonic waves by ultrasonic waves is set at 20 kHz. The same term ultrasound clearly indicates what is beyond (ultra) sound, identifying with the physical phenomenon only sound audible. For therapeutic purposes they are used for their effects: analgesic and anti-inflammatory; relaxant; fibronolitico and trophic. The ultrasound therapy can be performed with a technique in contact (with the interposition of a gel between the handpiece head and the skin) or submerged in the water when it comes to irregular surfaces such as hands and feet.