Imprecise output when calculating dBFS value from 16-bit audio sample value using C#

Question

I am calculating a dBFS value from a 16-bit wave file sample (-32768 to +32767) using c# as follows:

int sampleValue = -32700;

double dBFSvalue = 20 * Math.Log10(Math.Abs(sampleValue) / 32768);

But when I try to print the dBFS value, a sampleValue of 32768 results in "0" as it should, but any other value of sampleValue results in "-infinity".

MessageBox.Show($"Result: {dBFSvalue}dBFS");

Is this something to do with the displaying of type Double? How should I convert the number to display it properly in the form of "-60.5 dBFS"?

Thanks.

https://msdn.microsoft.com/en-us/library/system.string.format(v=vs.110).aspx — , Jul 14 '16 at 07:40

score 3 · Accepted Answer · answered Jul 14 '16 at 07:43

3

Replace your second line of code by

double dBFSvalue = 20 * Math.Log10(Math.Abs(sampleValue) / 32768.0);

You need the .0 to calculate it as floating point number. Otherwise it is calculated as integer and the term in the brackets is evaluated as 0.

answered Jul 14 '16 at 07:43

Fratyx

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Thank you! That was it. I've made that mistake before and I seem to keep forgetting. – Quantum_Kernel Jul 14 '16 at 07:45

Imprecise output when calculating dBFS value from 16-bit audio sample value using C#

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