High Quality Content by WIKIPEDIA articles! The sound barrier, in aerodynamics, is the point at which an object moves from transonic to supersonic speed. The term, which occasionally has other meanings, came into use during World War II, when a number of aircraft started to encounter the effects of compressibility, a collection of several unrelated aerodynamic effects that "struck" their aircraft like an impediment to further acceleration. By the 1950s, new aircraft designs routinely "broke" the sound barrier. At sea level the speed of sound is 340 meters per second which is about 760 miles per hour.