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Topic: Converting 16-bit values to dB (Read 4045 times) previous topic - next topic
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Converting 16-bit values to dB

Hello,

Does anyone know the proper way to get decibels from a 16-bit value?

I'm not sure if these assumptions are correct:
0x0000 = 0 dB
0xFFFF = 96 dB
0x???? = 48 dB

If anyone has more information on this, I'd love to hear it.

Thanks

Converting 16-bit values to dB

Reply #1 –
dB means different things to different people. I assume you mean something like dBFS.

the definition should be something like

db = 20*log10(X/0xFFFF)

If 0xFFFF is full scale.

0xffff = 0db
0x7fff ~= -6db
0x3fff ~= -12db
...
0x0000 = -Inf

Converting 16-bit values to dB

Reply #2 –
You might want to replace 0xFFFF with 0x8000.
0x8000 or 0x8000-1 can be considered "full scale" for 16 bit signed values.
be sure to pass only positive values to log10() then -- ie max(abs(signal)) for peaks
 

Converting 16-bit values to dB

Reply #3 –
Thanks Axon and Sebastian.  In this case the value is unsigned, although you're right, typically it's signed.

I may need to follow up on this later, not 100% sure I got it