Ultrasonic energy is mechanical energy as contrasted with other forms of energy such as nuclear particle radiation (x-rays, beta rays), electromagnetic energy (radio frequency waves, diathermy, microwave radiation), or invisible light (infrared, ultraviolet light waves). The source of ultrasonic energy is the ultrasonic transducer: a linear motor that converts electrical energy to reciprocating mechanical motion similar to a high-speed hammer. The motion occurs at a rate of 20,000 strokes or more per second, and is above the hearing range of the average person.

The ultrasonic mechanical motion, when propagated in air, is severely attenuated since air is an extremely poor sound transmission medium as compared to the metal and plastics in which it is intended to travel. Further, when the energy is propagated into a three dimensional space from a point source, it diminishes at a cubic rate each time the distance is doubled (i.e., every time the distance is doubled, 1/8 of the energy remains). The ultrasonic airborne energy is also absorbed into soft, non-reflecting materials (e.g., worker’s clothing or noise abatement foam materials). The remaining airborne ultrasonic energy is therefore diminished thousands of times as compared to the source.