Diachronic evolution of /e ɛ o ɔ/ in French across 100 years of speech archives

This study explores the diachronic variation of mid-vowel aperture (/e, ɛ, o, ɔ/) in word-final and penultimate-syllable positions in vowel harmony (VH) contexts in declamatory/journalistic French from 1925 to 2023. Our corpora include two pre-existing corpora – the INA broadcast archives corpus (1940–1999) and the ESTER corpus (2000–2004) – as well as two novel corpora, which include recordings from the Archives de la Parole by Hubert Pernot (1925–1929) and a selection from Radio France and YouTube spanning 2020 to 2023. Our results suggest a general tendency of VH weakening over the last century. Additionally, we found a significant acoustic convergence in terms of aperture between vowels /o/ and /ɔ/, but no convergence between /e/ and /ɛ/ in word-final position, contrary to prior research. An auxiliary imitation experiment was designed to investigate the correlation between the loud/projected voice in older recordings and the F1 of mid-vowels in VH contexts. The imitation experiment reveals a significant increase in F1 in loud declamatory speech. However, no effect of speech style on VH was observed, supporting the diachronic process of VH reduction.