Abstract:

Hearing aid (HA) users often have difficulty understanding speech in noise, and therefore noise reduction (NR) algorithms are implemented in modern HAs to attenuate background noise. However, spectral-subtraction-based NR, for instance, necessarily brings spectral distortion for speech cues that are essential for speech understanding, resulting in no clear benefit in speech intelligibility. Nevertheless, previous studies reported that attenuated noise provides cognitive benefits and increases the ease and comfort of listening. Also, HA users react differently to the trade-off between noise attenuation and spectral distortion. However, we do not know the neural mechanisms underlying NR's potential benefits and what drives the individual differences in those benefits. Here, I suggest a novel way to investigate NR benefits based on cortical dynamics of speech-in-noise processing with NR using high-density electroencephalography. First, we found that NR facilitated phonological processing across the left hemisphere dorsal-stream pathway; NR invoked stronger early responses in the supramarginal gyrus and weaker late responses in the inferior frontal gyrus compared to the no-NR condition. Second, calculating the amplitude ratio of the target word- and noise-evoked responses obtained from Heschl's gyrus allowed us to quantify individual listeners' speech unmasking ability, which predicted NR benefits. The present study takes a mechanism-based approach to HA outcomes and explores individual traits that may determine hearing intervention's success for a given listener.