Ultrasonics is a form of mechanical energy existing in a multitude of waveforms. It is used successfully in a wide range of applications, including almost every area of materials science such as medicine, metallurgy, cleaning, NDT, underwater sound, welding of plastics and metals, atomization of liquids, chemical effects, and cell disruption. There seems to be no end to its potential applications. The primary objective of this present chapter is to explain the criteria necessary to recognize the feasibility of applying ultrasonic energy to any application and to recognize its economic factors.