Setting a fixed scale for frequency analysis


I’m on Windows 7 Pro 64 Bit and use Audacity 2.2.2.
When I open an audio file (e.g. wav or mp3), I mark it and go to Analyze → Plot Spectrum (Frequency Analysis).
On the left there is a scale in dB.
My problem is that the first dB value is almost never the same when I check the frequencies of another audio file.
For audio file 1 it is -12 dB, for audio file 2 it is -10 dB, audio file 3 -50 dB etc.

I would like to use the frequency analysis to compare frequencies of different wav files.
Additionally, I would like to create screenshots and mix them together to have a better vision.
Right now I can’t do that because they don’t have the same relation point.
When mixing the screenshots, it would look as if all had an identical loudness.

Can you please add an option to give users the possibility to define a fixed dB value for the scale?
Even if I set 0 dB as start point and the loudest frequence is -50 dB (for example), I can live with the white space
between 0 dB and -50dB.
It would help me much more.

In this example, it would be more useful (for me) if the left pic has the same scale as the right one:

This is how I would like to have it:
(Just made it with Paint - probably it’s not exactly accurate):

Best regards

Here’s a free spectrogram-plugin which works in Audacity in Windows (& Mac),
where you determine the horizontal & vertical scales …

And there is a slimy way to get around this. Include a blast of 1KHz tone at -1dB at the beginning or the end of the show. Something obvious it’s not part of the actual performance. That tone should take over the display calibration.


Surely you’d be better with something inaudible, say 19kHz, then you can crop it out of far right of the spectrogram.
1kHz sine at -1dB will be a big spike in the middle of the spectrogram.

Oh, right.


How do I realize that simplest?
Adding a (white) noise, opening the EQ and lowering frequencies <19 kHz and <19 kHz?
Strangely the EQ doesn’t save the preset, so I can’t repeat the same EQing easily.

And the spectrogram-plugin looks like a real-time spectrogram.
I prefer Audacity’s one.


It displays Real-Time & average & max(imum) values …
SPAN - RealTme & MAX(imum) displays.gif