Spectral Entropy, with a choice of number of sub-bands. If one band, a measure of general peakiness of the spectral distribution.
See: SPECTRAL ENTROPY AS SPEECH FEATURES FOR SPEECH RECOGNITION Aik Ming Toh, Roberto Togneri and Sven Nordholm http://www.ee.uwa.edu.au/~roberto/research/theses/tr05-01.pdf
Pass an FFT in.
input fft chain, that is, from an FFT UGen
Size of FFT buffer must be known in advance for pre-calculation
Number of sub-bands for entropy calculation; spectral bins are collected in sub-bands, and the number of outputs of the UGen is numbands