This project investigated the impact of speaker-listener interaction on speech production. More specifically, it examined the strategies that adults use to clarify their speech when interacting with interlocutors  hearing them in difficult listening conditions.

A large set of recordings of spontaneous and read speech was collected for 40 monolingual English speakers. The spontaneous speech was produced while the participant completed ‘spot the difference’ picture tasks with another participant who was either hearing them normally or via a ‘communication barrier’ (a simulated cochlear implant, babble noise, or non-native speaker). Acoustic-phonetic measurements were made to investigate what aspects of the speech were enhanced in the different conditions.

We found that the strategies used by the speakers were well tailored to counteracting the specific impact of the different communication barriers; this shows that speakers are guided in their speech production by the communicative needs of their interlocutors. Individual speakers did vary both in the inherent clarity of their speech and in the speech enhancement strategies that they used, and the clarity of their speech was correlated across speaking styles. Finally, contrary to expectations, it was not the case that speakers who were more consistent or more extreme in the way in which they produce individual sounds were judged as being particularly clear.

Overall, these results support Lindblom’s Hyper-Hypo model of speech production, which claims that speech production is guided by listeners’ needs,  and provide of better understanding of how speakers use the control they have over their speech production to maximise communication effectiveness.