gms | German Medical Science

Recent advances in noise reduction (NR) signal processing have demonstrated benefits in speech-in-noise performance for hearing-aid users. To a lesser extent, listening effort has been evaluated so far in realistic scenarios with and without NR. Studies measuring listening effort using pupil dilations have found that less listening effort measured with activated NR might be associated with smaller peak pupil dilations (PPDs) [1]. This study goes one step further in relating such findings also to more audiologic parameters of hearing aid fitting, such as the acoustic coupling or the results in the suprathreshold Audible Contrast Threshold (ACTTM) Test.

Research questions: Can improved speech intelligibility and reduced listening effort, as indicated by smaller peak pupil dilations (PPDs), be measured with active NR? Is there a relationship between acoustic coupling, ACT-values and fatigue score?

Methods: Twenty-nine experienced hearing aid users participated in this study. To evaluate daily-life fatigue two questionnaires „Need for Recovery“ and „Checklist Individual Strength“ were completed by the participants. Participants performed a speech-in-noise task, by repeating German sentences from the Hearing in Noise Test (HINT, [2]) in presence of a masker consisting of a male speaker mixed with low-level speech-shaped noise. The test was carried out with NR in the hearing aids switched on and off. Both, PPDs and speech intelligibility were assessed.

Results: Speech intelligibility improved significantly with activated NR, regardless of acoustic coupling or ACT performance. Significantly smaller PPDs, indicating reduced listening effort, were measured with NR on compared to off. This result was independent of acoustic coupling and fatigue score. Poor ACT performers showed a larger listening effort improvement from NR than good ACT performers. The difference in PPD between NR on and off tends to be greater for the group with an open fitting compared to a closed fitting. A significant negative correlation between fatigue score and acoustic coupling was obtained.

Conclusions: Both speech intelligibility and listening effort improved with NR irrespective of acoustic coupling and general fatigue. Poor ACT-values indicated a larger improvement potential for hearing aid users, which may be an important finding for clinical practice. Further pupillometry studies should consider that, any hearing fatigue of the participant may have an effect on the pupil dilation and therefore on the results.