An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. Supersonic explosions created by high explosives are known as detonations and travel via supersonic shock waves. Subsonic explosions are created by low explosives through a slower burning process known as deflagration. When caused by a man-made device such as an exploding rocket or firework, the audible component of an explosion is referred to as its "report" (which can also be used as a verb, e.g., "the rocket reported loudly upon impact".)