levels - percentage and deciBels

QuadraphonicQuad

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bmnquad

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Jul 22, 2013
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I'm curious to know something more about level percentage and deciBels.

For example, Dolby Surround -3dB corresponds to 0.7071 power or 70.71%, right? It means that, given a 0dB level at 100%, -3dB is 29.29% lower.

Then:
100% ... 0dB
75% ... -2.5dB
50% ... -6.02dB
25% ... -12.04dB

Now, if I have a signal reduced at 25% of its original level, or -12.04dB, and I want it to be at 50%, should I increase it by +6.02dB? And to be at 75%, should it be +9.54dB?
 

DuncanS

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In Power terms its dB = 10log(P), so -3dB is 10^(-3/10)= 10^-0.3 = 0.5012 so 50%

Voltages etc. are expressed in dBs as 20log(V)
 
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