db'''dB(splSPL)''' =is an abbreviation for [[decibel]]s [[sound pressure level]]. It is sound output expressed purely as a pressure (force/area). It is used primarily by [[car stereo competitions]] to see whose can generate the "loudest" (more pressure) sound in closed car interior. They are measuring sound pressure. A [[sound engineer]] for a [[rock concert]] measures dB(watt) = dB(w) = dB(swl) and may increase power so the sound is still loud very far away.
Say they both generate an enormous 1000 acoustic watts = 150 dB(w). In a [[car stereo]] this is a painful level of about 165 dB(p). This same 1000 acoustic watts in a large [[stadium]] it is "diluted" to a nice but loud level of 100 dB(p). So depending on the environment the various sound dB levels change "BY THEMSELVES".
