Digital noise reduction: Outcomes from laboratory and field studies

The purpose of this study was to determine the impact of a digital noise reduction (DNR) scheme implemented in a current commercial hearing aid. In a double-blinded design, three conditions of onset time (4, 8, 16 seconds) were randomly assigned to the 25 subjects, plus one condition wherein the noise-reduction feature was disengaged. Subsequently, a fifth trial/condition, wherein the subject had access to three memories in which the different onsets were programmed, was carried out. For each of the five conditions, the subjects had an at-home trial, prior to obtaining self-report measures. Laboratory measures of speech perception showed no effect of the DNR, with or without the provision of visual cues. Laboratory-based ratings of ease of listening showed DNR-on (all onset times) to be rated significantly better than DNR-off; for ratings of listening comfort, the 4-second onset time was rated significantly lower (poorer) than the 8-second onset or the DNR-off condition; for ratings of sound quality, DNR-on or -off had no differential effect. Self-report measures indicated significantly higher aversiveness in the DNR-off condition compared to the pre-test scores