Ultrasonic waves are sound waves too high-pitched for human ears to detect. Their frequencies range from 20,000 hertz to about 10 trillion hertz (the maximum that modern ultrasonic generators are able to produce). Because ultrasonic waves are compressional, or pressure waves, with the ability to both shake and penetrate many materials, they have tremendous applications in industry and medicine.

A compression wave is created when a very dense material vibrates very fast. This causes the air around the material to be alternately pushed and pulled, producing regular pressure variations. At very high frequencies, such as the ultrasonic range, the compression wave can be focused into a fine "beam" which can then be used to vibrate particles in its path.

In order to generate an ultrasonic beam one must use a transducer—a device that converts electrical or magnetic energy into kinetic, or mechanical, energy. There are three methods for...