25 Hz noise

javiferferjaviferfer Tokyo
in Cyton

Hello,
I just bought the Ultracortex Mark IV and after implementing several experiments where I recorded the brainwaves of one participant while looking at images, the output I got is the one shown in the following image:

I understand the noise produced at 50 Hz but, what is the cause of the one at 25 Hz?
Thank you in advance.

Comments

  • wjcroftwjcroft Mount Shasta, CA

    Javier, hi.

    Are you using a notch filter at 50 Hz? Why does your FFT show the mains peak at approximately 52 Hz? Something must be off in your calculation. If you don't have a notch at mains, you could get subharmonics, such as at 25.

    https://www.google.com/search?q=subharmonics

    Additionally, you can plainly see mains harmonics noise in the Fp1 and 2 traces, as well as C3 C4.

    https://www.google.com/search?q=harmonics

    The CSV output from the GUI is raw, no filters have been applied.

    Regards, William

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