## Definitions

- f : spectrum frequency
- a : spectrum amplitude
- F0 : fundamental frequency
- F : harmonics frequencies
- A : harmonics amplitudes
- n : number of harmonics
- m : buffer size

## Timbre

## Sound width

*where k _{0} and k_{n} are the indices of the first and the last harmonics having an amplitude greater than a threshold.*

## Brightness

The brightness is calculated as the spectral centroid normalized by F0 :

## Tristimulus Coefficients

The Tristimulus coefficients are calculated as energy ratios of the first harmonics :

## Tonality Coefficient

The tonality coefficient is calculated as the Wiener entropy :

## Inharmonicity

The inharmonicity is calculated as the sum of harmonics frequencies deviations :

Refer to the bibliography for references.