Ada Biçer will defend her PhD Thesis “From Voice Cues to Voice Benefit: Voice Training, Intelligibility and Listening Effort in Cochlear Implant Listening”.

Supervisors: Prof. dr. ir. Deniz Başkent and Dr. Thomas Koelewijn

Abstract
When we listen to someone speak, we do not only process the meaning of their words but also the uniqueness of their voice. Familiar voices like those of friends and family, seem easier to understand than unfamiliar voices, especially during a group conversation. What makes voices for us familiar and whether listening to familiar voices is less effortful remains unexplored, especially for cochlear implant (CI) users.

In my PhD research, I investigated whether voice training can improve speech understanding and ease the cognitive demands of listening, otherwise known as listening effort. Across three studies, results from both normal hearing listeners and CI users were assessed, using the pupil dilation response as an objective measure for listening effort. I found that voice training did reduce the effort required to understand speech. This effect was found for both normal hearing listeners and CI users, and across different voice training methods. Nevertheless, voice training did not lead to improvements in speech understanding.

These findings suggest that voice training can be beneficial at a cognitive level, which is not always reflected in behavioral outcomes. This is especially important for CI users, for whom everyday listening situations are generally experienced as effortful, which can lead to fatigue. Findings from these studies highlight the importance of measuring not just how well people understand speech, but also the cognitive cost associated with it. Future research can assess whether voice training could be incorporated into auditory rehabilitation.