the sound barrier
noun [ S ] uk/ˈsaʊnd ˌbær.i.ər/ us/ˈsaʊnd ˌbær.i.ɚ/
声障，音障（指飞行物的速度达到音速时所产生的气动阻力急剧增大）
a large increase in the force opposing a moving object as its speed reaches the speed at which sound travels
There is usually a sonic boom when an aircraft breaks the sound barrier. 飞机冲破声障时，通常会产生音爆。