Expressions (phrases, clauses, etc.), Noun
1. sound barrier
Wikipedia definition
2. Sound barrierThe sound barrier, in aerodynamics, is the point at which an aircraft 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 planes like an impediment to further acceleration. By the 1950s, new aircraft designs routinely "broke" the sound barrier.
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