Overall good answers that give someone just getting into acoustics a good starting point. Since you're a declared audiophile and I used to be an acoustic engineer for Harman, I'm going to correct this statement. The scale is exponential, however 3dB is NOT twice as loud. To increase output by 3dB requires twice the power (not twice as loud). In reality 3dB is a noticeable increase in volume, but not significant. Twice as loud is a bit harder to measure as it relies on the human ear which isn't as easy to measure as a piece of equipment. However, it's commonly accepted that something being twice as loud is an increase of 10dB.