How to eliminate potential AC noises?

[DaohanZhang]

Hello everyone! I found my last NPX recording got polluted with some potential AC noises possibly due to poor GND and REF. Here are some of the noises after sorting with KS4, which is spikes approximately appeared at at 50Hz pulses. Is there any preprocess filters could eliminate such noises. I tried using notch_filter centered 50, 100 and 150Hz before default bandpass_filter, it just did not work.

[alejoe91]

Hi @DaohanZhang

Can you plot a spectrum of the traces? If the noise is localized, you can play with the q factor of the notch filter to broaden/narrow the notch band to try to remove most of the noise

[DaohanZhang]

It's a little bit weird... I have put most of the details on slack.

[alejoe91]

It would be helpful to look at the spectra though (couldn't find them on slack)

[DaohanZhang]

Here comes the spectra!
First I plot the traces and there are periodic patterns:

After that, I plot the spectra of some of the elecs:

[alejoe91]

Thanks, can you also plot the power spectrum density? It makes it easier to check for very localized noise sources. From the spectrograms, they seem quite distributed so a notch filter won't help much here...

[DaohanZhang]

These are PSDs

[alejoe91]

@DaohanZhang

Can you try a notch filter where you have the peak (~5000Hz) and see if it improves the situation?