The Interaction between Reverberation and Hearing Aid Processing for Speech Perception in NoisePublic Deposited
Inability to understand speech in the presence of background noise is one of the most common complaints of individuals with hearing impairment. Two hearing aid processing strategies specifically recommended for improved speech perception in noise include: digital noise reduction (DNR) and cognition-based wide dynamic range compression (WDRC) speed. While previous studies have found that these processing recommendations provide benefit under laboratory conditions, that work did not account for reverberation which is present to varying extents in most everyday listening situations, and which disrupts the transmission of important acoustic cues involved in hearing aid signal processing. The first set of experiments examined acoustic and perceptual effects of DNR under a range of reverberant conditions in older adults with hearing impairment. Participants listened and responded to speech-in-noise processed with simulated reverberation and DNR processing. While DNR processing had minimal effect on speech intelligibility without reverberation, speech intelligibility was substantially lower with DNR processing in reverberant conditions. Unlike in the anechoic condition, listeners reported no subjective benefit with DNR processing in reverberant conditions. These findings were consistent with acoustic analyses showing that acoustic benefit of DNR processing decreased with increasing degrees of reverberation. The second set of experiments examined acoustic effects of WDRC under a range of reverberant conditions in older adults with hearing impairment and whether listeners benefitted from different WDRC speeds based on working memory (i.e., cognition-based WDRC speed). Consistent with previous findings, in the absence of reverberation individuals with high working memory performed better with fast-acting WDRC, whereas individuals with low working memory performed better with slow-acting WDRC. However, this effect was diminished in mildly reverberant conditions and eliminated at greater amounts of reverberation. These findings were consistent with acoustic analyses which showed that the acoustic difference between fast-acting and slow-acting WDRC decreases with increasing degrees of reverberation. These experiments provide evidence that reverberation alters hearing aid signal processing in such a way that may diminish the perceptual benefits of some processing strategies (cognition-based WDRC speed) or even produce adverse perceptual effects (DNR). Overall, these findings suggest that the benefit experienced by listeners in the real world may vary based on the reverberant characteristics of a given listening situation.