Most work investigating the role of convergence in situations of language attrition has focused on the morpho-syntactic restructuring of the dying language variety. A central concern of such research has been untangling the factors driving the restructuring with an eye towards establishing whether the changes observed are best viewed as externally driven or, by contrast, as internally motivated. A second and equally important concern of this research attempts to define the domains of the linguistic system that may be the most permeable to external influence. The present study provides a contribution to this line of research and sheds light on its two leading concerns from the domain of phonology and phonetics. Specifically, we present the results of an instrumental study of the phonological vowel system of Frenchville French and argue that this linguistic variety is undergoing a perceptually striking process of phonetic convergence with English that is motivated by the auditory and acoustic similarity between a subset of vowels in the contact languages. An interesting consequence of our analysis is that bilingual phonologies may become particularly permeable to inter-linguistic influence precisely where they are acoustically and perceptually unstable, and where they are already congruent to some degree.