Reverse engineering a digital filter
Signal 1 was an average of a left and right signal and signal 2 was a binocular signal.

I followed the suggestion of MBaz, and computed the frequency response of the filter for each segment (N = 3) for each subject (N=12).  Then I averaged the frequency responses of the filters. Here is the result:


MBaz and Matt: Thank you so much for solving my problem.
Matt, it looks close to your filter.
Lee