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.
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. They led to prohibition of routine supersonic flight over land. Although they cannot be completely prevented, research suggests that with careful shaping of the vehicle, the nuisance due to the sonic booms may be reduced to the point that overland supersonic flight may become a feasible option.
A sonic boom does not occur only at the moment an object crosses the speed of sound; 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 travelling at supersonic speeds. But it 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.
Explanation:
As incredible as the Concorde was, the sonic booms created by its supersonic flights were so disruptive that most countries restricted or completely prohibited the aircraft from flying over land. The sonic boom, at its worst, would be heard as a very loud thunder clap that was right overhead. The force of the boom rattled windows and loosened roof tiles. But even when the sonic boom sounded like a “softer” distant thunder clap, it was distracting to people and caused disruption of sleep and interruptions in activity.
Imagine that you are driving on your way to work, and with clear skies overhead, you suddenly hear the sound of thunder. Your immediate responses are most likely surprise, shock, and an instinctive search for the source. Being caught by surprise in certain situations is rather annoying, and in others, potentially dangerous.
In 1964, the FAA and NASA conducted a six-month sonic boom research project in Oklahoma City – without warning residents beforehand. The experiment consisted of eight sonic booms, every day, for six months. 15,000 complaints and a class action lawsuit were filed. The government lost on appeals. Great idea, guys, just brilliant.
When the Concorde was originally designed, in the early 1960s, governments and airlines around the world lined up to place orders. The plane did an around-the-world publicity trip, and was well-received. But as awareness of the sonic boom effect grew, almost every country banned the aircraft. Only the US, Great Britain, and France allowed the Concorde to enter their airspace, and then only to cities in close proximity to the ocean – NYC, London, Paris, and Washington, DC.
The Concorde was specifically designed for supersonic flight (specifically, Mach 2) and was very fuel-inefficient at subsonic speeds (less than Mach 1). Unfortunately, it was thus not feasible to fly at supersonic speed over water and then at subsonic speed over land.
What causes a sonic boom?
When any object moves, it creates waves in front of and behind it. Think of the waves that a boat creates at its bow and stern. In front, the waves are compressed together as the boat sails forward. Behind, the waves spread out away from the boat. In this case, you only see the waves on the surface of the water, and it appears two-dimensional.
Similar principles are at play with aircraft. In front of the nose of a plane, air is pushed together and compressed as the aircraft flies forward. Behind the plane, the air creates waves that radiate out and away in the shape of a cone – three-dimensionally.
