[Eeglablist] Persistent 20 Hz Harmonic Line Noise in EEG Data

[Евгений Машеров]

And another naive (and almost offensive) guess: Could the power line filter have accidentally switched from 60 Hz to 50 Hz? This can happen when restoring the factory settings after a failure. I'd start by checking this possibility, even if I consider it unlikely.

> Dear EEGLAB List,
> 
> I am currently dealing with persistent line-noise contamination in my EEG
> recordings, specifically strong peaks around 20 Hz and its harmonics (40
> Hz, 60 Hz, etc.). The contamination remains substantial even after multiple
> preprocessing attempts.
> 
> Raw Data PSD for reference: https://urldefense.com/v3/__https://ibb.co/5WbNqYCW__;!!Mih3wA!EfdhaFV_tpprT4Wc8_HcfK7KDVTXA0O0NPLW3Ws732nxP-TmPxHUXI_qXevcPIO8hfndJk8euI6BWbB1_dCuBxHG_A$
> 
> I have already tried:
> 
> -
> 
> Average re-referencing before notch filtering
> -
> 
> Average re-referencing after notch filtering
> -
> 
> Multiple full-rank average reference implementations, including:
> -
> 
> Makoto’s fullRankAveRef()
> -
> 
> Manual full-rank average reference using (nchan + 1) denominator
> 
> Despite this, a large amount of the harmonic noise is still present in the
> spectra.
> 
> For reference, the issue looks somewhat similar to this discussion:
> https://urldefense.com/v3/__https://mne.discourse.group/t/line-noise-eeg/11817__;!!Mih3wA!EfdhaFV_tpprT4Wc8_HcfK7KDVTXA0O0NPLW3Ws732nxP-TmPxHUXI_qXevcPIO8hfndJk8euI6BWbB1_dB2ZPVDPg$
> 
> I would greatly appreciate advice on how people in the EEGLAB community
> typically handle this kind of persistent harmonic contamination.
> 
> Would you recommend CleanLine, Zapline-plus, spectrum interpolation, ASR,
> ICA-based approaches, or something else?
> 
> Thank you very much for your help.
> 
> Best regards,
> Maeghal Jain
> BISE Lab
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