What actually is the sound barrier?
Until 1947, no pilot had ever flown at 700 miles an hour and lived to tell about it. The airplanes designed in the early 1940s shuddered and shattered as they reached what we call the speed of sound. Many people despaired and said that no plane would ever fly faster than this mysterious sound barrier. The sound barrier and the thermal barrier are problems for the experts who design fast planes. Both of these barriers are related indirectly to the speed of sound and the way in which sound travels through the air. A sonic boom from a high flying jet tells us that the aircraft has reached a speed as fast or faster than the speed of sound. It has broken through the sound barrier. A plane at supersonic speeds must also cope with the thermal or heat barrier. If the plane is not properly designed, the heat caused by supersonic shock waves may melt the metal on its nose and wings. Sound travels out from a vibrating object in waves. Its pulsing energy keeps pace with the vibrating drum or other
