Comment by mrob

A 3dB increase is a doubling of a power quantity, but you need 6dB to double a root-power quantity (formerly called a field quantity). Sound pressure is root-power quantity:

https://en.wikipedia.org/wiki/Power,_root-power,_and_field_q...

Consider a loudspeaker playing a constant-frequency sine wave. Sound pressure is proportional to the excursion of the cone. To increase sound pressure, the excursion has to increase, and because frequency is fixed the cone will have to move faster. If it's covering twice the distance in the same time interval it has to move twice as fast. Kinetic energy is proportional to the square of velocity, so doubling the sound pressure requires four times the power, and doubling the power only gets you sqrt(2) times the sound pressure.

Human loudness perception generally requires greater than 6dB increase to sound twice as loud. This depends on both frequency and absolute level as you mentioned, with about 10dB increase needed to double perceived loudness at 1kHz and moderate level.