The following outlines the process NeuroScore uses to calculate the power in a given frequency band.
First, the Periodogram is calculated to compute the power values within discrete frequency intervals.
For example, if the sampling rate of the signal is 250 Hz and the Periodogram is calculated with a 10th order FFT (1024 samples), then the resolution will be 250/1024 = ~ 0.244 Hz.
The first value in the Periodogram will then encompass the power between 0 Hz and 0.244 Hz, the second one will encompass the power between 0.244 and 0.488, etc…
The power within a given frequency band is the sum of all successive Periodogram values from the starting frequency to the end frequency.
Note: The first and the last values taken into account will have a special treatment because only a fraction of them will be summed.
Highlighted below, NeuroScore calculates the power from the Theta band (between 4 and 8 Hz) of the first 10 seconds of data as 8.722E-10 V2.
This was calculated by first calculating a Periodogram of the signal (sampled at 250 Hz) using a 10th order FFT (0.244 Hz resolution). The 4-8 Hz output of the Periodogram is below:
The power bands are calculated from this output using the following method: