text: what is the difference between "supersonic" and "ultrasonic"?   "supersonic"  supersonics, branch of physics dealing with the phenomena arising when the velocity of a solid body exceeds the speed of sound in the medium, usually air, in which it is traveling.                 "ultrasonic" ultrasonics, branch of physics dealing with high-frequency sound waves, usually in the range above 20,000 hertz (hz), that is, above the audible range.