[Mne_analysis] notch filter for removing power chord signal

Hari Bharadwaj hari at nmr.mgh.harvard.edu
Wed Sep 12 23:29:38 EDT 2012
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Hi Denis,
   The multitaper based rmlinesc() routine in Chronux to remove line noise
works well:
http://www.chronux.org/downloads/chronux/chronux/documentation/chronux_2_00/spectral_analysis/continuous/rmlinesc.html

The following is a reference that describes the technique:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1300074/

Also, most of the time I don't remove it so when I do time-frequency
decompositions I know that I have the scales correctly done when I see the
line components at the correct frequency..

Regards,
Hari



On Wed, September 12, 2012 10:27 pm, sheraz at nmr.mgh.harvard.edu wrote:
> Hi Denis,
>
> As Alex said SSP cant be used to remove line frequency, as its comes from
> electronics.
>
> If you go mne-Matlab way, you can use eegfilt to have notch filter or try
> harmonics filter which works better for line frequency. For reading and
> writing raw fif file look at mne_ex_read_write_raw.m.
>
> sheraz
>
>
>
>> 2012/9/12 Alexandre Gramfort <gramfort at nmr.mgh.harvard.edu>:
>>> hi Denis,
>>>
>>>> I wonder whether there is a MNE-way of removing power-chor artifacts
>>>> from wide-band MEG data (1-200 Hz).
>>>
>>> you mean the AC current and the harmonics of 50 or 60Hz?
>>
>> yes.
>>
>>>
>>>> As there does not seem to be a notch filter available, empty room SSPs
>>>> might be the way to do it.
>>>
>>> yes don't use SSP for this.
>>>
>>
>> ok, thanks though
>>
>>> You need a notch like filter but I am not aware of any with mne or
>>> mne-python.
>>>
>>> Alex
>>>
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-- 
Hari Bharadwaj
PhD Candidate, Biomedical Engineering,
Boston University
677 Beacon St.,
Boston, MA 02215

Martinos Center for Biomedical Imaging,
Massachusetts General Hospital
149 Thirteenth Street,
Charlestown, MA 02129

hari at nmr.mgh.harvard.edu
Ph: 734-883-5954





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