Export log frequency spectrum

Audacity 3 Help Forum Windows
1

I plotted a frequency spectrum and want to export it with the currently selected settings:

Hamming window,
1024 window size,
Log frequencies

However, when I export the spectrum to a text file, it seems that my settings are ignored, since the frequencies are not given with a log scale. Is it possible to export the spectrum with a log scale? If not, how can I calculate the log spectrum from the exported values?

I’m using Audacity 2.0.5

2

The log scale in Plot Spectrum is just the way that the graph is plotted. The data from which the graph is plotted is the same regardless of the graph scale. The data comes from the FFT analysis, which produces the number of bins according to the FFT size (for a size of 1024 there will be 511 frequency bins because the DC bin is not included).

3

Thanks for the clarification. I want to use the exported file to plot the spectrum in gnuplot. Do you know how exactly the log scale is applied on the plot? Simply taking the log of the amplitude in dB will obviously not work (negative log).

4

Never mind, I thought that the log scale was applied to the amplitude (y-axis) instead of the frequencies (x-axis). Thanks anyways.

5

Use the command “logscale”
For example, if you want the frequency on a base 10 logarithmic scale:

set logscale x 10

Then plot the graph.

There is a Gnuplot command reference here: http://www.gnuplot.info/docs_4.0/gpcard.pdf

6

Thanks steve, will use that.