[timgr]

Maybe this is clearer - depending on your math savvy.

The actual unit is the bel, named for Alexander Graham Bell. The decibel is one tenth of a bel.

All calculations are done in base 10, thus log10(10) = 1 and 10^log10(10) = 10.

Decibels from voltage, dB = 20 log10(V1/V2)

Decibels from power, db = 10 log10(P1/P2)

Recall that P = V^2/R, so power goes like the square of the voltage. That's where the extra factor of 2 comes from.

So to get percentages from dB, find V1/V2 or P1/P2.

V1/V2 = 10^(dB/20), then (V1/V2 - 1) * 100 = voltage change in percent.

hth!

Note that your calculator likely has a "log" button (base 10) and a "ln" button (base e, the natural log), and a corresponding 10^x and e^x button respectively.