Ultrasound means mechanical vibrations with a frequency higher than the human can detect, i.e. over 20 kHz (20000 ), although the frequency used for the therapy ranges between 0,75 and 3 MHz. Ultrasound therapy is used to treat tissue and skin. Ultrasound in therapeutic doses acts as a heated micro massage. Ultrasound emits electric vibration that improves blood flow and nutrition of tissues, and has spasmolytic and analgesic effects.