A vowel fractal dimension study

Fractal dimension (D) estimates the degree of freedom in a signal, which allows a good approach of its fluctuations. Using 16 kHz time sampling and the box-counting method we studied Ds of some of the main stationary parts of the speech, ie the French phonemes [a], [e], [i], [o], [y] pronounced 4 times by 10 males and 10 females. Our study consistently demonstrates that the stationary signal of vowels is not fractal, but shows the possibility to design at smallest scales a kind of signature for each vowel, despite that presently this categorisation is not totally significant. As box counting method objectives and quantifies the roughness of the signal, this procedure may be useful for clinical applications. Moreover, in case of dysphonia, these signatures could be perhaps included in the cochlear implants speech signal processing.