I recently started working on sleep study.
For my research I download sleep EEG data from physionet. The EEG data has 100 Hz sampling rate and was recorded from 2 bipolar EEG site.
When I start the preprocessing stage, I encounter a simple problem:
How would I know if my signal has an artifact or noise?
It should be noted, based on Nyquist theorem and my signal's sampling rate, the maximum frequency of my signal is 50 Hz, so I did not filter unnecessary EEG frequency.
In general I only used a simple notch filter at 50 Hz, and used simple threshold method in order to remove the epochs that were grossly contaminated by muscle and/or eye movement artifacts.
Back to the main question, how should I know if I need to uses more complicated method for removing EMG or EOG artifact from my signal?