Kevin - yes dBa is a log scale. No, increasing by 1dB on a log scale isn't 2x. Log scales go like this:
3dB = 2x
6dB = 4x
9dB = 8x
10dB = 10x
13dB = 20x
20dB = 100x
etc.
Remember dBa is a measure of the sound
intensity, which isn't the same as "loudness".
What you may be thinking of is the
Bel scale (Lw(a)). It is also a log scale, but created for "loudness" measurements. 1 Bel = 10dBa.
ps - now go read the other thread I linked to bro
