Ultrasound (US) is a mechanical (not electrical) form of energy, and therefore, strictly speaking, it is not really electrotherapy at all, but it falls into electrotherapy. Ultrasound is applied using the head of an ultrasound probe that is placed in direct contact with your skin via a transmission coupling gel. this probe is having electricity as a basic source of energy, which is being converted into mechanical forms into sound or we can say waveforms energy. The sound energy is known as mechanical vibration at increasing frequencies. The normal range of human sound is from 16 Hz to something close to 15-20,000 Hz (in kids and young adults). Beyond that upper limit, the ultrasound is known as the mechanical vibration. Usually, the frequencies used in therapy vary from 1.0 and 3.0 MHz (1 MHz= 1 million cycles per second). Sound waves are longitudinal waves consisting of compression and rarefaction zones. Particles of material will oscillate about a fixed poin...