Noise & ~65hz interference

tmorrilltmorrill
edited October 2017 in Cyton


Hi all,

I am posting two questions here:
1) It appears that there is some noise in channels 3, 7, 10 (especially), 13, and 16. Does this look like noise or actual brain readings? I've been using the headset for a couple months now and I remember the headset showing all channels around 5-15uVrms. Looking back over my past recordings, it seems to have gotten worse over time.

image

2) There appears to be interference at 65hz. You can see I have the notch filter at 60hz so it shouldn't be from power lines. Is there something emitting a 65hz signal from a Macbook Pro?

Not sure if this is a valid thing to look at but I also put the headset on a flat surface near my Macbook and the front of the headset (closest to the Macbook) is showing some noise. When I move it away from the computer, the noise seems to disappear with the headset off of my head, but when I move away from the computer with the headset on I still see issues in the channels mentioned above.

image

I appreciate any help or tips.

Thank you,

Todd 

Comments

  • wjcroftwjcroft Mount Shasta, CA
    Todd, hi.

    Sometimes various electronics, LED / CFL lighting, power supplies, etc., might generate spurious EMF noise. The 65 is an odd-ball number. Have you tried running your tests in another room / building, or away from equipment that might be creating the noise? 

    Your GUI snapshots show noise on all channels, more than you should be getting. When noise or signals appear on all or most channels at once, this is usually a sign that your Reference ear clip electrode (the one common electrode shared with all channels) is suspect. Try swapping the two ear clips. Oddly, @GeneralFox has seen some similar noise issues. See his recent thread.

    Mentioning @openbci.

    William

  • tmorrilltmorrill
    Hey William - nicely done. As best I can tell the Hue Phillips lights next to my desk were the culprit. I'll also add, as I'm sure you know, you really need to wait a few minutes for the headset to settle and the impedance to come down before you get valid recordings. Not sure if you have any tips on this. I'd really like to be able to quickly generate a lot of high fidelity short clips (e.g. meditation).  When setup takes ~15 minutes it sort of deters me from recording.

    I still haven't figured out the 65hz signal. It is in my apartment because when I stepped just outside the front door it went away. Will report back if I figure it out. Cheers.

    image
  • GeneralFoxGeneralFox
    Hi,

    I used a Frequency Counter that I purchased for $30 off the Internet and swept my apartment to find the best location.

    Funny bit was - it was right where I was already sitting! 

    Thanks,
    Don
  • wjcroftwjcroft Mount Shasta, CA
    Don, was it a "frequency counter" or an EMF meter? The meter is what is required for an assessment of EMF noise. AND... there is a wide range of EMF meters out there. Some just measure 50 or 60 hz. Some are directional. The ones that measure microwave band emissions from wifi, cell towers, phones, etc. -- also vary widely in their capabilities.

  • GeneralFoxGeneralFox
    William,

    Good catch!  It is marketed as a Frequency Counter, but truly it is in fact an RF Meter.  Sorry for not being more clear. 

    I was amazed at all of the RF generated by hydro lines hidden in the walls of my apartment.  I found my stereo generating a significant amount of noise, but only if you were very close to it.  I picked up a new monitor, to reduce on the amount of noise generated by my workstation, and moved my computer farther away from me.

    Thanks,
    Don
  • pushtheworldpushtheworld
    @GeneralFox can you post a link of this device you bought? I want!
  • wjcroftwjcroft Mount Shasta, CA
    There are a huge range of these devices.

    I had an electrosensitive friend (a craniosacral practitioner) who used the HF35C,


    Her office was right across the street from an office building with cell antennas all around the top edges. And at least one of those was pointed directly at her location. She ended up installing some conductive cloth shielding on her walls / curtains until she finally moved to another better location.

    I have had a Trifield meter for decades, although these are only good for power mains detection.


    You'd probably find some relevant reviews on Amazon,

  • GeneralFoxGeneralFox
    edited November 2017
    Hi @tmorrill,

    I just wanted something that basically detected signals - nothing too precise - I wanted to keep costs reasonable. 

    I picked up one of these for around $40.00 CDN:
    https://www.ebay.com/itm/1x-IBQ102-Portable-Hand-held-Frequency-Counter-10Hz-2-6GHz-For-Two-Way-Radio-B1-/262969082025

    I'm able to detect the signals generated by my monitor, hydro, stereo, cell phone, and etc...  How accurate is it?  Well, probably not perfect for $40.  How good is the detection?  Well, it is not using the best antenna considering all of the available frequencies that it detects.  But does it work?  YES!

    Thanks,
    Don
  • GeneralFoxGeneralFox
    Hi @pushtheworld  @wjcroft,

    A question in general - if EMF noise plays a significant factor in this - would we benefit from wearing grounding straps?  The body is a giant antenna, so if we were to ground ourselves via a strap, could that not eliminate stray electrical signals in our uncontrolled environments (meaning we are not in an electrically controlled environment and thus, subject to stray electrical signals)?

    Thanks,
    Don
  • wjcroftwjcroft Mount Shasta, CA
    Don, hi.

    EMF magnetic fields from mains noise or other field emitters goes EVERYWHERE. (But limited by inverse square law.) Grounding straps can drain off some (usually) static electric field potentials. Which is why they are wisely employed when soldering or placing sensitive IC components. So the main advice if you are seeing significant mains or other EMF evidence in your EEG, is to reposition yourself out of the field.

    It is still a good idea, if you are in a cold, dry winter environment -- with say wool rugs or other static charging potential -- to discharge yourself (on a grounded surface) before touching any electronics. Especially exposed circuit boards.

    William

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