The Spell research on the phonetic segmental aspects of speech is focused on the class of vowels. The aim of this aspect of the Spell project is to succeed in indicating to a given speaker speaking a non-native language (Italian, French, or English (American English and British English RP)) how to improve the pronunciation of vowels belonging to the non-native vowel system. In order to automatically provide the information needed to improve the pronunciation, a vowel representation capable of guiding the speaker must be selected. Two different vowel representation strategies, based on two different normalization methods, were implemented. An analysis of the efficiency of these procedures within the Spell system in the case of the Italian vowel system is reported.