DBSPL

dB(SPL) is an abbreviation for decibels 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".

Sound can be a pressure; dB(p) or a watt dB(w) or a velocity dB(v). Conveniently, they are very closely equal and interchangeable below 120 dB. Above 120 dB it should be expressed as a pressure dB(p) or a sound wattage dB(w). 95% of all sound meters measure pressure. Special Computer controlled sound meters or programs may give you a dB(watt) level they can be found at: http://www.makeitlouder.com/Computer%20Software.html

External links

For a detailed explanation visit and read near the 80% bottom of the page; http://www.makeitlouder.com/Calibration.html

For more read appendix in the middle 55% of this page; http://www.makeitlouder.com/Decibel%20Level%20Chart.txt