Auditory processing for speech in noise is enhanced in hearing aid users

Hearing impaired people typically experience more difficulty when listening to speech in noisy situations than normal hearing people. However, it is still unclear where this increased effort originates. Electrophysiological measures were used to examine differences between auditory processing and lexical processing. Neural entrainment, a measure of synchronization between an auditory stimulus and neural brain activity, has previously been shown to be greater for intelligible speech and when a listener is focusing attention. It can thus be expected that relative to a normal hearing group, a hearing impaired population would show reduced neural entrainment in connection with poorer speech recognition performance and higher listening effort. However, with our study we demonstrated the opposite; in a speech-in-noise task with different levels of multi-talker babble noise, the hearing impaired group had significantly higher entrainment than the normal hearing group, despite similar or even poorer levels of speech recognition. Based on our findings, we suggest that higher entrainment in the hearing impaired group might reflect that more auditory processing is required to understand speech in noise.