I have been using the Equalizer tool to clean up some frequency peaks and troughs for a few FLAC files.
The question I have is what is the Q factor applied to each equalizer band? I have assumed this is a fixed value as the tool is none parametric.
Appreciate any comments on this.
I presume you are referring to the “Graphic Eq” mode, in which case the q factor is approximately 4.3 for a gain change of 6 dB.
Assuming a sample rate of 44100 Hz, the graphic Eq is a 1/3rd Octave 31 band graphic. “1/3 Octave” refers to the “half gain width”, which for band gain of 6 dB works out as a q factor of 4.318477. I don’t think you can convert exactly between half gain width and q because they are measuring different things. The q factor measurement is traditionally based on the 3 dB gain width, which is obviously meaningless if the band gain is small. Trying to calculate the exact value is complicated further by implementation details and settings. The equalization effect in Audacity is an FFT filter, so the frequency response is affected by the filter width, particularly for low frequencies. Also, the Graphic mode offers three different “interpolation” methods which have subtle effect on the result (see above link).