Source: http://www.sengpielaudio.com/calculator-db.htm

This chart illustrates the relationship of changes in level as measured in decibels (dB). It takes a 10-dB change to double the perceived loudness, but only a 6-dB change to double the sound pressure. To double the power requires only a 3-dB change. Stated another way, it takes 10 times as much power from an amplifier to double the perceived sound.