How to avoid vowel normalization in identification of vowels in continuous speech

The examination of the diagrams showing the unnormalized formant frequencies in the F1-F2(first and second formant) plane of the vowels (in italian or other languages) shows an overlap of the regions characteristic of each vowel (vowel zones) caused mainly by the differences in the measurement and shape of the vocal tract among speakers. In this paper, a method is presented that makes possible the evolution of the vowel zones by using an adaptive procedure. At the beginning of the algorithm, the center of gravity of each vowel zone represents the mean characteristics for many speakers, when pronouncing each vowel. In the successive steps, the centers of gravity and the shape of the zones tend towards the ones characteristic of the specific speaker. Results are given that show this evolution both for male and female speakers, with the elimination of the overlap between the zones.