I am having the FFT results of two distinct voice signals. Let's say the FFT results of these two signals are of the form (a+ib) and (c+id). Now, I want to calculate the PSD of each signal and also the Cross PSD between them. I'm calculating PSD and Cross PSD as follows.
PSD of signal 1 = a * a + b * b;
PSD of signal 2 = c * c + d * d;
Cross PSD between signal1 and signal2 = (ac - bd) + (ad + bc). I also want to know whether this equation represents cross-correlation or cross PSD?
And also, I have ambiguity about the importance of cross PSD. I know that cross PSD is obtained by taking the Fourier transform of the cross-correlation results. I know that from PSD, we can get an idea of the power for different frequencies present in the signal. How does cross PSD differ from PSD? I found out that by using cross PSD, we can find the power shared by a given frequency for the two signals. How do we know how much power is shared between the two signals from a single constant power value per frequency? Please help me out in understanding what the cross PSD means and what is its importance?