1 Hz - 100 Hz limits on spectrogram

Feedback and Reviews for Audacity 2.x
Forum rules
This board is ONLY for general feedback and discussion about Audacity 2.X.

If you require help, or think you have found a "bug", please post on the forum board relevant to your operating system.
Windows
Mac OS X
GNU/Linux and Unix-like
Post Reply
jbeale
Posts: 5
Joined: Sat Dec 30, 2017 11:46 pm
Operating System: Windows 10

1 Hz - 100 Hz limits on spectrogram

Post by jbeale » Tue Mar 27, 2018 2:34 pm

Audacity 2.2.2 on Windows 10. This is a great program! ...with a few annoyances...as with previous versions, if I enter a Spectrogram Settings start frequency below 1 Hz or end frequency below 100 Hz it doesn't work. I get a warning dialog such as "Maximum frequency must be 100 Hz or above" or "The minimum frequency must be an integer."

I am using Audacity to display infrasound spectra, meaning below 20 Hz, and as low as for example 0.01 Hz. For now I am rescaling my sample rate up to avoid the limit. It would be nice if those limits did not exist (a feature request). Obviously sub-Hz spectra can be displayed by the program, given that the Analyze/Plot Spectrum feature does so when the larger FFT sizes are selected. Thank you for considering! -john

steve
Site Admin
Posts: 47283
Joined: Sat Dec 01, 2007 11:43 am
Operating System: Linux *buntu
Contact:

Re: 1 Hz - 100 Hz limits on spectrogram

Post by steve » Tue Mar 27, 2018 4:10 pm

jbeale wrote: I am using Audacity to display infrasound spectra, meaning below 20 Hz, and as low as for example 0.01 Hz.
I'm sure that you will agree that is unusual.

The minimum frequency for spectrogram settings when "linear" scale is selected is 0 Hz.
0Hz cannot be represented on a logarithmic scale because log0 is undefined.

100 Hz as the minimum upper limit is an arbitrary figure that is generous for "audio" analysis. This only affects the default setting for the track, and you can override it by zooming in closer (vertically) after making the settings. However, I notice that there appears to be a bug in the track spectrum view which gives incorrect values when looking at extremely low frequencies. I'll log this as a bug.

I don't know why the developer decided that the scale range settings have to be integers. Perhaps because for normal audio use, a decimal value would most likely be a user mistake (such as trying to type 2.5 as a kHz value rather than 2500). I'm just guessing on this one as it seems like an arbitrary and not useful restriction to me.
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)

jbeale
Posts: 5
Joined: Sat Dec 30, 2017 11:46 pm
Operating System: Windows 10

Re: 1 Hz - 100 Hz limits on spectrogram

Post by jbeale » Mon Apr 23, 2018 11:45 pm

No doubt it is an unusual application; thanks for considering at any rate. I suppose if you allow fractional frequency, you also have to deal with such things as whether the decimal place is indicated by "." as in the US or "," as in some other countries.

Post Reply