As these waves pile up, a very large pressure difference exists across the wave-front, which is called a shock wave. An object traveling through the air causes sound wave energy (air) to pile up along a conical line (like the bow wave of a boat) called a wave-front. Initially, you hear nothing because the plane is moving faster than the sound itself but when the sound pressure cone arrives at your ear you hear a boom. Consider a supersonic aircraft flying toward you while you look up at it from the ground.

When an aircraft is flying at supersonic speeds the sound pressure forms a cone whose vertex is at the nose of the plane. This conical bow-wave visible on the surface of water, called a wave-front, is similar to an airplane’s sonic boom. The boat pushes the water and a wave crest goes out from the bow of the boat and spreads across the lake. Imagine a boat traveling through the water. Thus Mach 3 means three times the speed of sound. The Mach number is the speed of the object divided by the speed of sound. Often supersonic speeds are referred to in terms of a Mach number. There is a noticeable increase in the aerodynamic drag on the plane at this point, hence the notion of breaking through the 'sound barrier.' When a plane exceeds the speed of sound it is said to be supersonic. The compressed air in front of the plane exerts a much larger than usual force on the plane. As the plane approaches the speed of sound, it approaches this invisible pressure barrier set up by the sound waves just ahead of the plane. The air in front of the plane exerts a force on the plane impeding its motion. As the plane approaches the speed of sound, the sound pressure 'waves' pile up on each other compressing the air.

The waves propagating in front of the plane get crowded together by the motion of the plane. Exactly why is this speed called the sound barrier?Ī plane produces sound that radiates out from the plane in all directions. At 68° F the speed of sound is about 343 m/s or 767 mph at sea level. The speed of a sound wave actually varies with temperature and air density, increasing about 0.6 m/s for every Centigrade degree temperature increase. The speed at which sound travels is known as the sound barrier. Chuck Yeager fired the X-1 engine and was accelerated past the sound barrier becoming the first man to travel faster than the speed of sound. On October 14, 1946, a small, almost rocket type plane called the Bell X-1 was dropped from a large B-29. What happens when something breaks the sound barrier? April 2001 Vocatio Center for Life Calling and Career.Office of Student Leadership & Engagement.

Bullet crack sound effect