The effect of degraded speech stimulus on listening effort in individuals with normal hearing

Listening effort can define as the deliberate allocation of cognitive resources to overcome obstacles in goal pursuit when performing a task. Reduced quality of incoming sound may increase the listening effort required to understand speech. The speech signal coming through the cochlear implant has lower acoustic-phonetic details in both spectral and temporal dimensions than the normal speech. This study aims to evaluate the effect of auditory spectral resolution on listening effort in cochlear implant simulation. Twenty-one normal-hearing participants aged between 24-25 years listened to normal speech (NS) and CI simulations with 12, 8, 6, and 4 numbers of spectral channels. In the study, a dual-task paradigm was used. The secondary task was a rhyme judgment. In the response time measurements between NS-6 channels, NS-4 channels, 12-6 channels, 12-4 channels, 8-6 channels, 8-4 channels, and 6-4 channels, in the pupil size measurements between NS-12 channel, NS-8 channels, NS-6 channels, NS-4 channels, 12-4 channels, 8-4 channels and 6-4 channels significant differences were found. As the number of channels decreased, response time and pupil size increased. As a result, as the number of channels decreases, the increase in response time and pupil size is interpreted as the effect of spectral resolution on listening effort.