Effects of Digital Noise Reduction Processing on Subjective and Objective (Pupillometry) Assays of Listening Effort

Background/Objectives: Although research has demonstrated the positive impacts of hearing aid (HA) digital noise reduction (DNR), limited research is available on the impacts of the strength of DNR on listening effort. This study evaluated the effects of changes in the strength of HA DNR on listening effort, measured, behaviorally, using a self-report rating scale, and, physiologically, using pupillometry. The agreement between both measures was also examined. Methods: Eleven young adults with normal hearing completed a sentence-in-noise recognition task. Stimuli were processed through four noise reduction conditions (off, minimum, medium, maximum) using DNR algorithms found in conventional digital HAs. After sentence presentation, participants subjectively rated their perceived listening effort. Pupillometry was recorded during the task to assess changes in pupil size (a proxy of listening effort) during sentence recognition. Results: Participants' perceived listening effort reduced as the noise reduction strength increased from off to medium DNR and then plateaued for the maximum DNR condition. Pupil dilation increased from off to medium DNR and then reduced for the maximum condition. Correlation analyses suggested no agreement between self-report and pupillometry measures of listening effort. Conclusions: Both self-report and pupillometry measures demonstrated changes in listening effort, with changes in the DNR strength indicating that noise reduction systems do provide benefit in reducing listening effort to a certain extent. Lack of agreement between the measures suggests that both methods might be assessing different constructs of listening effort and care should be taken while making methodological decisions to assess listening effort in individuals wearing HAs.