ultrasonic (adj.)

word-forming element meaning "beyond" (ultraviolet) or "extremely" (ultramodern), from Latin ultra- from ultra (adv. and prep.) "beyond, on the other side, on the farther side, past, over, across," from PIE *ol-tero-, suffixed form of root *al- "beyond." In common use from early 19c., it appears to have arisen from French political designations. As its own word, a noun meaning "extremist" of various stripes, it is first recorded 1817, from French ultra, shortening of ultra-royaliste "extreme royalist."

"done by means of sound waves," 1923, from Latin sonus "sound" (from PIE root *swen- "to sound") + -ic. Sonic boom "shock wave from an aircraft exceeding the speed of sound" is attested from 1952.