Vowel Reduction in Conversational Speech: the case of reductions in French

Reduction, particularly in the context of connected speech, plays a crucial role in shaping the distinctiveness and spectral properties of vowels, reflecting the dynamic adaptability of language in communicative settings. This study investigates the characteristics of vowels within spontaneous French conversations, with a primary focus on reduction phenomena. Employing both a controlled and a conversational dataset, our exploration extends beyond vowel reduction in conversations to more controlled production settings in addition to encompassing various reduction forms (lexicalized and non-lexicalized reductions), aiming to discern whether the reduction in vowel properties is related to the frequency of these reduction forms. Our findings revealed that within conversational contexts, vowels have reduced distinctiveness, evident in smaller Vowel Distinctiveness Index (VDI) values and elevated centralization values (aFCR) while exhibiting smaller Vowel Spaces, indicative of a reduction in spectral properties. The correlations between vowel reduction and the other reductions showed a lack of statistical significance, suggesting that lexicalized and non-lexicalized reductions are likely governed by a distinct set of linguistic and contextual variables. Our findings indicate that vowel characteristics undergo notable reductions as the speaking context shifts from controlled conditions (such as isolated vowels or monosyllabic words) to conversational settings. This reduction is manifested by larger Vowel Spaces and greater distinctiveness (VDI) in controlled contexts, contrasting with the decreased vowel distinctiveness and higher centralization ratios observed in conversational speech, highlighting the dynamic nature of spoken language production and its adaptability within varying communicative contexts.