sound barrier Name for the cause of an aircraft's difficulties in accelerating to a speed faster than that of sound. When approaching the speed of sound, an aircraft experiences a sudden increase in drag and loss of lift. These are caused by the build-up of sound waves to form shock waves at the front and back of the aircraft. The problems were solved by designing aircraft with smaller surface area, swept-back wings, and more powerful engines. See also sonic boom

sound bar·ri·er • n. (the sound barrier) the increased drag, reduced controllability, and other effects that occur when an aircraft approaches the speed of sound, formerly regarded as an obstacle to supersonic flight.