We look at the power spectrum. Pay attention to the spectrum analyzer and oscilloscope displays. Notice where the slow waves are, where the fast are. Focus on the tallest bars and try to make them go down just by looking at them. Record a couple minutes of data.
a. The spectrum analyzer should be set to show to 60Hz. Especially look for very tall bars at 50 or 60 that don’t seem to change much or for very tall spikes that occur at regular intervals on the spectrum. These are indications of electromagnetic artifact—electrical environmental noise masquerading as EEG.
b. The oscilloscope should show a waveform with a variety of amplitudes (heights) and a variety of widths (frequencies). The more regular and consistent it is, the more likely it is not coming from the brain. Sharper wave tops and bottoms are more likely artifact than rounded ones.