How to filter noise in EMG signal - Tibialis anterior muscles

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Mounia Bob
Mounia Bob on 22 May 2022
Answered: Star Strider on 22 May 2022
Hello everyone
I am trying to filter an EMG record for a healthy subject. I eliminate bias and rectified the signal. I converted it to frequency domain but I am stuck with how to eliminate noise/ what filter to use/ what is the appropriate cut off frequency..?
Can someone help me witht this?

Answers (2)

Image Analyst
Image Analyst on 22 May 2022
You can just zero out the data beyond where you think it's all noise, then inverse transform. But it looks like the noise is pretty much the same in every frequency range so that will still leave the noise in the signal region, though it should look a little better. Can you indicate what the signal would look like if it had no noise whatsoever? Like draw on it with a red pen or something. You can perhaps smooth the signal to get what you like using a sliding polynomial fit with a Saivtzky-Golay filter, sgolayfilt

Star Strider
Star Strider on 22 May 2022
First, before calculating the fft, subtract the mean of the signal to eliminate the D-C (0 Hz) spike so the other peaks are more easily identifiable.. However there appears to be broadband noise, so it is unlikely that a frequency-selective filter can eliminate it. The best option is to use the Savitzky-Golay filter (sgolayfilt) to eliminate as much of the broadband noise as possible since a frequency-selective filter will not have any significant effect on broadband noise.

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