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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US">Hello Hasnae,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">The Fieldtrip’s FAQ might provide you with an answer:
<a href="https://www.fieldtriptoolbox.org/faq/why_is_there_a_residual_50hz_line-noise_component_after_applying_a_dft_filter/">
https://www.fieldtriptoolbox.org/faq/why_is_there_a_residual_50hz_line-noise_component_after_applying_a_dft_filter/</a></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">. An alternative to the DFT filter is the bandstop filter.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">As mentioned in the webpage:
<a href="https://www.fieldtriptoolbox.org/faq/what_kind_of_filters_can_i_apply_to_my_data/">
https://www.fieldtriptoolbox.org/faq/what_kind_of_filters_can_i_apply_to_my_data/</a></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> , you can apply padding to make the DFT filter sharper. I am not sure if this would help you, but you
can play with the padding and see if your results improve.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">All the best,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">Konstantinos Tsilimparis<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> fieldtrip <fieldtrip-bounces@science.ru.nl>
<b>On Behalf Of </b>AGOURAM Hasnae via fieldtrip<br>
<b>Sent:</b> Wednesday, July 10, 2024 2:26 PM<br>
<b>To:</b> fieldtrip@science.ru.nl<br>
<b>Cc:</b> AGOURAM Hasnae <hasnae.AGOURAM@univ-amu.fr><br>
<b>Subject:</b> [FieldTrip] Issue with DFT filter used to remove power line noise at 50 Hz<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black">Hello everyone,
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black">I am having a small issue with the DFT filter used to remove power line noise at 50 Hz. Even after applying the filter, I still observe line noise in the power spectral density.<br>
<br>
I am using the </span><a href="https://www.fieldtriptoolbox.org/reference/preproc/ft_preproc_dftfilter" target="_blank"><b><span style="font-size:13.0pt;font-family:"Arial",sans-serif;color:#0097A7">ft_preproc_dftfilter</span></b></a><span style="font-family:"Calibri",sans-serif;color:black">
function from the Fieldtrip toolbox, which applies a narrow-band notch filter to eliminate the 50 Hz noise.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
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<p><span style="font-family:"Calibri",sans-serif;color:black">Here is the snippet of code I am using<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-family:"Calibri",sans-serif;color:#006FC9">%filtre the data
</span></b><b><span style="font-family:"Calibri",sans-serif;color:black"><br>
</span></b><b><span style="font-family:"Calibri",sans-serif;color:#006FC9"> cfg = [];</span></b><b><span style="font-family:"Calibri",sans-serif;color:black"><br>
</span></b><b><span style="font-family:"Calibri",sans-serif;color:#006FC9"> cfg.hpfilter = 'yes'; % High-pass filter</span></b><b><span style="font-family:"Calibri",sans-serif;color:black"><br>
</span></b><b><span style="font-family:"Calibri",sans-serif;color:#006FC9"> cfg.hpfreq = 1 ; % High-pass frequency</span></b><b><span style="font-family:"Calibri",sans-serif;color:black"><br>
</span></b><b><span style="font-family:"Calibri",sans-serif;color:#006FC9"> cfg.dftfilter = 'yes'; % enable notch filtering to eliminate power line noise</span></b><b><span style="font-family:"Calibri",sans-serif;color:black"><br>
</span></b><b><span style="font-family:"Calibri",sans-serif;color:#006FC9"> cfg.dftfreq = [50]; %set frequencies for notch filtre</span></b><b><span style="font-family:"Calibri",sans-serif;color:black"><br>
</span></b><b><span style="font-family:"Calibri",sans-serif;color:#006FC9"> dataContinuousResampled_filtred = ft_preprocessing(cfg,dataContinuousResampled);</span></b><b><span style="font-family:"Calibri",sans-serif;color:black"><br>
</span></b><b><span style="font-family:"Calibri",sans-serif;color:#006FC9"> </span>
</b><span style="font-family:"Calibri",sans-serif;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black">If you have any suggestions, please let me know.
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-family:"Calibri",sans-serif;color:black">Hasnae Agouram<br>
PhD student</span></b><span style="font-family:"Calibri",sans-serif;color:black"><o:p></o:p></span></p>
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