Sonic boom

For other uses, see Sonic Boom.

The sound source is travelling at 1.4 times the speed of sound (Mach 1.4). Since the source is moving faster than the sound waves it creates, it leads the advancing wavefront.
A sonic boom produced by an aircraft moving at M=2.92, calculated from the cone angle of 20 degrees. Observers hear nothing until the shock wave, on the edges of the cone, crosses their location.
Mach cone angle
NASA data showing N-wave signature.[1]
Conical shockwave with its hyperbola-shaped ground contact zone in yellow

A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to the human ear.

The crack of a supersonic bullet passing overhead or the crack of a bullwhip are examples of a sonic boom in miniature.[2]

Sonic booms due to large supersonic aircraft can be particularly loud and startling, tend to awaken people, and may cause minor damage to some structures. This led to the prohibition of routine supersonic flight overland. Although sonic booms cannot be completely prevented, research suggests that with careful shaping of the vehicle, the nuisance due to sonic booms may be reduced to the point that overland supersonic flight may become a feasible option.[3][4]

A sonic boom does not occur only at the moment an object crosses the sound barrier and neither is it heard in all directions emanating from the supersonic object. Rather, the boom is a continuous effect that occurs while the object is traveling at supersonic speeds and affects only observers that are positioned at a point that intersects a region in the shape of a geometrical cone behind the object. As the object moves, this conical region also moves behind it and when the cone passes over the observer, they will briefly experience the "boom".

  1. ^ Haering, Edward A. Jr.; Smolka, James W.; Murray, James E.; Plotkin, Kenneth J. (1 January 2005). "Flight Demonstration Of Low Overpressure N-Wave Sonic Booms And Evanescent Waves". AIP Conference Proceedings. 838: 647–650. Bibcode:2006AIPC..838..647H. doi:10.1063/1.2210436. hdl:2060/20050192479. S2CID 109622740. Archived from the original on 13 February 2015.
  2. ^ May, Mike (September 2002). "Crackin' Good Mathematics". American Scientist. 90 (5): 415–416. JSTOR 27857718.
  3. ^ "Back with a boom? Supersonic planes get ready for a quieter, greener comeback". Horizon (online magazine). Retrieved 6 May 2021.
  4. ^ "Fixing the Sound Barrier: Three Generations of U.S. Research into Sonic Boom Reduction and what it means to the future" (PDF). Federal Aviation Administration. 21 April 2010. Retrieved 5 May 2021.