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.
Severn bore of the flood tide, the bore is accompanied by a rapid rise in water level which continues for about one and a half hours after the bore has passed. The Severn bore is not a self-reinforcing solitary wave or soliton but rather a shock wave which is formed because the wave is travelling faster than the wave speed in water above the bore (see tidal bore for more details). The passing of the bore causes a churning of the water, and the myriads of tiny bubbles popping contributes much of the roaring sound made by the bore. The largest recorded