Sonic boom is sufficiently long. A new metric has emerged, known as "perceived" loudness, measured in PLdB. This takes into account the frequency content, rise time, etc. A well-known example is the snapping of one's fingers in which the "perceived" sound is nothing more than an annoyance. The energy range of sonic boom is concentrated in the 0.1–100 hertz frequency range that is considerably below that of subsonic aircraft, gunfire and most industrial noise. Duration of sonic boom is brief; less than a second, 100 milliseconds (0.1 second) for most fighter-sized aircraft and 500 milliseconds for the space shuttle or Concorde jetliner.
Explosive within the substance (usually below 1000 m/s) in contrast to detonation, which occurs at speeds greater than the speed of sound. Deflagration is a characteristic of low explosive material. This term is used to describe an explosive phenomenon whereby the decomposition is propagated by an explosive shock wave traversing the explosive material at speeds greater than the speed of sound within the substance. The shock front is capable of passing through the high explosive material at supersonic speeds, typically thousands of metres per second. In addition to chemical explosives, there are a number of more exotic explosive materials, and exotic