Shock wave cannot travel any further upstream and the pressure progressively builds in that region; a high pressure shock wave rapidly forms. Shock waves are not conventional sound waves; a shock wave takes the form of a very sharp change in the gas properties. Shock waves in air are heard as a loud "crack" or "snap" noise. Over longer distances, a shock wave can change from a nonlinear wave into a linear wave, degenerating into a conventional sound wave as it heats the air and loses energy. The sound wave is heard as the familiar "thud" or "thump" of a sonic boom,
Anti-shock body Anti-shock body An anti-shock body (also known as Whitcomb body or Küchemann carrot) is a pod positioned on the leading edge or trailing edge of an aircraft's aerodynamic surfaces to reduce wave drag at transonic speeds (Mach 0.8–1.0). Most jet airliners have a cruising speed between Mach 0.8 and 0.85. Wave drag can be minimized, for aircraft operating in the transonic regime (Mach 0.8–1.0), by having a cross-sectional area which changes smoothly along the length of the aircraft. This is known as the area rule, and is the operating principle behind the design of anti-shock bodies. Reducing wave drag improves