When measuring brainwaves, it’s fundamental to get a clear signal with minimal noise. I usually discard all the sessions that exceed a certain noise threshold, because noise can distort the information we need to analyze.
There are some aspects to take into consideration when trying to get a good signal.
- Headset Design: A well-designed and securely fitted EEG headset typically results in lower noise levels. It is also more resilient to slight head movements.
- Type of Activity Recorded: The type of activity being recorded is the second factor. The ideal activities are those where the subject is still, like meditation, studying, reading, watching TV, etc.
- Electrical Interference: The third factor that I usually encounter is external electrical interference. Being aware of and minimizing such interference is important for accurate readings.
Even though I use it all the time, I have to admit that the Muse 1 headset (and likely the Muse 2 as well, since the design is similar) has some trouble securing sensors behind the ears (TP9 and TP10). That might’ve been the reason why the Muse S model was created. To enhance the stability of the Model 1, I put a sports headband on top of the EEG headset, making sure that it applies some pressure in the ears area.
Don’t allow the headband to apply so much pressure that it becomes uncomfortable for you. If the headband feels too tight, consider stretching it slightly until some fibers crack, loosening the fit.
Type of Activity Recorded
Browsing the brainwaves journal, you will notice that my recorded activities are mostly stationary. While I would love to track myself doing activities like exercise, I know those sessions would have to be discarded.
Even driving, during which I was mostly stationary in my seat with little head movement, has resulted in high noise levels and high delta brainwave levels, which I attribute to artifacts introduced by the vibrations of the car.
Other sessions were too important to discard completely but since the back signals had so much noise, I had to analyze to clean front signals only.
The point is that when analyzing brainwaves with a Muse headband, we are limited by the activities we can measure.
Once the points above are taken care of, you should be able to see a similar signal on the Mind Monitor app. Ideally, each of the four signals will display low amplitude, and the voltage numbers on the top-left screen will exhibit minimal variation, typically within a range of a few dozen values rather than multiple dozens or hundreds.
If, after doing everything right, you still can’t get a signal as clean as this, you might be dealing with some electrical interference. In this case, I assess my environment and make the necessary changes. While I don’t have a predefined procedure, it usually involves me sitting in a different place, not holding my phone, not touching or turning off certain objects, and things like that.
How To Check for the Session Noise Levels?
After recording the session with the Mind Monitor app, you can upload the generated file to the Meditation Monitor site and choose the Variance metric. If all signals are shown below the Max Variance on the graph, then you can consider your session to have a clean signal.
And that’s how you know if you have a proper signal that is ready to be analyzed.
Sound Engineering and Research @ SonoFields