# spectralEntropy

Spectral entropy for signals and spectrograms

## Description

specifies options using one or more name-value arguments.`entropy`

= spectralEntropy(`x`

,`f`

,`Name=Value`

)

`spectralEntropy(___)`

with no output arguments plots the
spectral entropy. You can specify an input combination from any of the previous syntaxes.

If the input is in the time domain, the spectral entropy is plotted against time.

If the input is in the frequency domain, the spectral entropy is plotted against frame number.

## Examples

## Input Arguments

## Output Arguments

## More About

## Algorithms

The spectral entropy is calculated as described in [5]:

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

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.

## References

[1] Pan, Y. N., J. Chen, and X. L. Li.
"Spectral Entropy: A Complementary Index for Rolling Element Bearing Performance Degradation
Assessment." *Proceedings of the Institution of Mechanical Engineers, Part C:
Journal of Mechanical Engineering Science*. Vol. 223, Issue 5, 2009, pp.
1223–1231.

[2] Sharma, V., and A. Parey. "A
Review of Gear Fault Diagnosis Using Various Condition Indicators." *Procedia
Engineering*. Vol. 144, 2016, pp. 253–263.

[3] Shen, J., J. Hung, and L. Lee.
"Robust Entropy-Based Endpoint Detection for Speech Recognition in Noisy Environments."
*ICSLP*. Vol. 98, November 1998.

[4] Vakkuri, A., A. Yli‐Hankala, P.
Talja, S. Mustola, H. Tolvanen‐Laakso, T. Sampson, and H. Viertiö‐Oja. "Time‐Frequency
Balanced Spectral Entropy as a Measure of Anesthetic Drug Effect in Central Nervous System
during Sevoflurane, Propofol, and Thiopental Anesthesia." *Acta Anaesthesiologica
Scandinavica*. Vol. 48, Number 2, 2004, pp. 145–153.

[5] 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*.

## Extended Capabilities

## Version History

**Introduced in R2019a**

## See Also

`kurtogram`

| `pspectrum`

| `spectralKurtosis`

| `spectralSkewness`

| `spectralSpread`

(Audio Toolbox)

### Topics

- Spectral Descriptors (Audio Toolbox)