The term sonic boom is commonly used to refer to the shocks caused by the supersonic flight of an aircraft. Sonic booms generate enormous amounts of sound energy, sounding much like an explosion. Thunder is a type of natural sonic boom, created by the rapid heating and expansion of air in a lightning discharge.
When an object passes through the air, it creates a series of pressure waves in front of it and behind it, similar to the bow and stern waves created by a boat. These waves travel at the speed of sound, and as the speed of the object increases, the waves are forced together, or compressed, because they cannot “get out of the way” of each other, eventually merging into a single shock wave at the speed of sound.
This critical speed is known as Mach 1 and is approximately 1,225 kilometers per hour (761 mph) at sea level at room temperature.
Probably the smallest sonic boom is produced by the whip’s crack.
Other great pictures on this site and on this next video: