Spectral entropy for audio signals and auditory spectrograms

The spectral entropy is calculated as described in [1]:

$$\text{entropy}=\frac{-{\displaystyle \sum _{k={b}_{1}}^{{b}_{2}}{s}_{k}\mathrm{log}\left({s}_{k}\right)}}{\mathrm{log}\left({b}_{2}-{b}_{1}\right)}$$

where

*s*is the spectral value at bin_{k}*k*.*b*_{1}and*b*_{2}are the band edges, in bins, over which to calculate the spectral entropy.

[1] Misra, H., S. Ikbal, H. Bourlard,
and H. Hermansky. "Spectral Entropy Based Feature for Robust ASR." *2004 IEEE International Conference on Acoustics, Speech, and Signal Processing*.