spectral whitening

[John8974]

I try to do spectral whitening through msnoise1.6 and have some questions.

I saw a reference that bandpass filter as 0.04-1.25Hz and spectral whitening as 0.05-1Hz.

In MSNoise, there are parameters related to whitening, which are 'whitening' and 'whitening_type', but I am not sure the way to assign the whitening frequency (0.05-1Hz).

The definition of whitening is related to autocorrelation, none, or components not the frequency.

I saw the table definition about low and high filter, 'the lower/upper frequency bound of the whiten function', but I guess it is not the parameter related to whitening but just a filter.

So could you please let me know the way to assign whitening frequency?

[ThomasLecocq]

Hi,
The whitening frequencies are indeed defined in the filter's parameters as "low" and "high", here 0.05 and 1.0 Hz, respectively. They act both as a bandpass within those bounds, and a whitening (all to 1.0, or PSD, or else depending on whitening_type).

Thomas

[John8974]

I am trying to follow some references related to effects of earthquakes on ambient noise and in some reference, they used different bandpass filter, spectral whitening frequency, and mwcs_low/high frequency.

I am not sure the reason they set all frequencies differently but know how to handle bandpass filter and mwcs_low/high frequency, so that is why I wondered the way to control spectral whitening.

Now I understand the 'low' and 'high' filter act as both of bandpass and whitening. Thank you for your help.

p.s. I saw the psd plot. If I want to plot it, do I need to set the whitening type as psd?

[ThomasLecocq]

What do you mean "the psd plot" ? The psd-spectrogram ? That is generated using the latest msnoise dev version from github (using msnoise qc compute_psd etc), and has nothing to do with PSD-Whitening (which is just another method for whitening the spectra)

[John8974]

Yes the psd-spectrogram. I got it.
I am using MSNoise 1.6.1 and when I do msnoise qc compute_psd, the error (No such command 'qc') occurs. And when using 'msnoise', there is no command for it. Is it possible to use the command in MSNoise 1.6.1? Or for that, is there anything that I should install or do something ? If it is possible, it would be useful for analyzing data.

[ThomasLecocq]

no, as I said above, the PSD stuff is only available in the development version, i.e. here on github. You'll want to install msnoise from source (=here), but be aware that this dev version is not compatible with the 1.6.2 version (changes in the database schema, new config elements, etc).

[John8974]

I see. Thank you so much for your help!!