Dear all, I plotted that channel spectra of my unfiltered continuous raw EEG data and found the line noise at 60 Hz. But there are also spikes at 50, 70, and 80 Hz. I'm wondering what those noises might be. Thanks! Here is a link to the plot: https://docs.google.com/drawings/d/1LtkAMscOYzSH5f-r-0O0mweastJsFqyUZNhzclXb_EQ/edit?usp=sharing Best, Chao