Measure of spectral complexity

Looking at the page:

http://web.gfi.uib.no/~ngbnk/kurs/notes/node123.html

I find a set of formulae that make a measurement of coherence expressed
as a "coherence spectrum" analogous with a correlation coefficient. I'm
tempted to adopt the above measure until I get further through Bendat
et. al's books.

Cheers,

Ross-c

I am a beginner here , so take my analysis with a grain of salt. I
would think the highest complexity is associated with randomness since
essentially you cannot compress any of the information . This might
mean that if you take the inverse FFT of your spectrum, then the
autocorrelation of that would be sharply peaked around zero.

Best