Current age and language use impact speech-in-noise differently for monolingual and bilingual adults

Purpose: Some bilinguals may exhibit lower performance when understanding speech in noise (SIN) in their second language (L2) compared to monolinguals in their first language. Poorer performance has been found mostly for late bilinguals (L2 acquired after childhood) listening to sentences containing linguistic context, and less so for simultaneous/early bilinguals (L2 acquired during childhood) and when testing context-free stimuli. However, most previous studies tested younger participants, meaning little is known about interactions with age; the purpose of this study was to address this gap.Method: Context-free SIN understanding was measured via the Modified Rhyme Test (MRT) in 3836 young and middle-aged bilingual and monolingual adults (ages 18–57; 19.5% bilinguals, all L2 English) with normal to near-normal hearing. Bilingual adults included simultaneous (n = 466), early (n = 185), and late (n = 97) bilinguals. Performance on the MRT was measured with both accuracy and response time. A self-reported measure of current English use was also collected for bilinguals to evaluate its impact on MRT performance.Results: Age impacted MRT accuracy scores differently for each listener group. Relative to monolinguals, simultaneous and early bilinguals showed decreased performance with older age. Response times slowed with older age at similar rates for all groups, despite faster overall response times for monolinguals. Among all bilingual listeners, greater current English language use predicted higher MRT accuracy. For simultaneous bilinguals, greater English use was associated with faster response times. Conclusions: Speech-in-noise outcomes in bilingual adults are impacted not only by fixed features of their language history (i.e. age of acquisition) but also by language practices which can shift over time (i.e. current language use), supporting routine querying of language history and use in the Audiology clinic.