When an aircraft flies at supersonic speed it produces a boom corridor some 60 to 100 kms wide in which the pressure experienced on the ground rises very sharply to a higher value through a shock wave. The pressure then drops until it is approximately as much below ambient pressure as it was above it. A second shock wave brings the pressure back to its normal atmospheric value. While absolute pressure change on the ground caused by the shock wave is relatively small, its onset is very rapid, creating a characteristic sharp report that is known as the sonic boom, and which can be heard (depending on atmospheric conditions, location of observer, flight altitude, or ground configuration), as anything between a sharp crack of a rifle shot and a distant rumble of thunder.
Available evidence points to sonic booms as the source of considerable annoyance and complaints in the communities exposed to them at frequent and regular intervals. Sonic booms startle, interfere with sleep and concentration, cause irritation and affect people's aesthetic enjoyment of life. Sonic booms cause damage to property, particularly windows and plaster. The effects of sonic booms on the natural environment (particularly on triggering snow avalanches and injecting water vapour into the atmosphere) also pose problems.
Although supersonic aircraft have flown for over thirty years, until now they have not affected a significant portion of man's environment. This is because the use of supersonic aircraft has been largely limited to military aviation and their unintended effects on the environment in the form of sonic booms have been sporadic and confined, in most countries, to relatively small and isolated areas of land. The introduction of the supersonic aircraft into commercial service adds a new dimension to the problem.