Spectrogram Questions


#1

Hey guys. Some questions. So I got my muse a few months ago and didn’t have time to play around with it. I made some spectrogram with muse and the data looks a bit weird.
It seems there is quite some difference between each channels.
To clarify a little, the temperature of the color corresponds to the log(amplitude), vertical axis corresponds to 0-110Hz, and horizontal axis corresponds to time.
The graph is computed with 50% overlapping half sine window of 32 samples, padded to 128 samples before DFT.

The other question is that it’s pretty clear that there are “horizontal lines” that “cuts” the graph into small stripes, does anyone know why?

eeg2

eeg3

eeg4

eeg1


#2


#3

Hi there,

The way the data looks depends on the setup of the recording and what happens during it, so it’s difficult to tell from a spectrogram if something is wrong without that context. How did you make the recording? Were you wearing the headband, and if so, what were you doing while recording? Do you know which plots correspond to which channel?

In general terms, it looks like you have two pairs of channels, one pair having more wide band noise than the other. This could make sense as the ear channels tend to look quite different than the forehead channels but similar to each other, and vice versa.

The stripes you’re referring to just look like a signal with some harmonics. Hard to know without also looking at the time domain signal.


#4

Thanks. That makes sense. I just realized that the stripes at the center seems to be the 50/60Hz AC power supply (harmonics at 100 ish). All I remember is that the the strongest graph is eeg/3.
My other concern is eeg/3 is so much stronger than the other graphs…Maybe I didn’t wear it properly.
I recorded the graph while wearing it and staring at the spectrogram in real time. I’ll try to get a better graph sometime…