It is a unit of measurement of sound pressure level. Acoustic sound pressure levels ((SPLs) measured in dB are commonly referenced to a level of 20×10-6 Pa (pascal) or 20 µPa. This is the sound level of the threshold of human hearing. The SPL in decibels is the number of decibels above this threshold.
Examples:
A conversation at 1 m distance -> -> 60 dBSPL, Rock concert -> -> 110 dBSPL and jet takeoff at 450 m -> 120 dBSPL.
The threshold of human hearing is 0 dBSPL and the threshold of pain is 130-140 dBSPL.
