Thank you very much! You really made my day!

This was the missing link to my question. I just integrated your code and am able to see quite precise values in the range from 60dB (A) to 100 dB(A). Therefore, a corrective value for $DBA_MIC_FS was integrated in the upper part of the code.

my  $DBA_MIC_FS = -110;

[download]

Now, the values are similar compared to a standard sound meter Class 2. There are some problems with the USB mic, though: There are no smaller values as 60 db(A)… this was tested on Windows with the same mic… no lower values than 60 dB(A) :-(

This leads to the idea, that USB mics are not built to measure sound pressure levels precisely, but more to record human voice. Additionally considering the good advice from stevieb, USB mics seem to be a dead end for noise measurements (ot this 10 EUR mic is just not good enough for this purpose)

So, there will be a test with another USB mic and if there are similar problems, I might switch to analog mics with ADC technology. But this is out of the scope of this forum, I suppose...

In reply to Re^2: Measuring the sound level (dB(A)) with PERL by John-Robie
in thread Measuring the sound level (dB(A)) with PERL by John-Robie

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