Using Alpha-Band Power to Evaluate Hearing Aid Directionality Based on Multistream Architecture.

Purpose: The aim of the study was to evaluate whether behavioral speech-in-noise (SiN) benefits of hearing aid directivity based on multistream architecture (MSA) might result in reduced electroencephalographic activity in the alpha-band, as is often associated with task difficulty.

Method: A single-blind within-subject design was used in this study. Thirteen older adults (M_age = 73.5 years, range: 62-82 years, six women) with sensorineural hearing loss participated in the study. Participants wearing study hearing aids first performed an adaptive sentence-level SiN test in an MSA-enabled condition (i.e., MSA-ON) to determine the signal-to-noise ratios (SNRs) corresponding to speech reception thresholds for 50% correct performance (i.e., SRT-50s). Participants were then tested at their individualized SNRs with target sentences alternating on each trial between two loudspeakers positioned in the front at 0° and -30° azimuth, such as to simulate turn-taking between two talkers seated across from the listener. Electroencephalographic activity was recorded as participants performed this SiN test in two hearing aid conditions: MSA-OFF and MSA-ON.

Results: Neural oscillations in the alpha-band were significantly reduced over centroparietal electrode sites when listeners performed SiN testing in MSA-ON versus MSA-OFF conditions. Alpha-band power was also observed to increase significantly over the course of 60 test trials, possibly indicative of listener fatigue. Reductions in alpha-band power were not significantly related to likewise improvements in SiN performance.

Conclusions: Hearing aid directivity based on the MSA algorithm resulted in significantly lower neural activity associated with listening task difficulty in a simulated multitalker situation. Although these results align with the behavioral SiN improvements associated with MSA, magnitudes of change in alpha-band power did not correlate with the degree of behavioral benefit at the level of individual listeners. Measuring neural oscillations in the alpha-band might be useful for evaluating and gaining greater insight into the impact of hearing aid processing on listening effort in challenging acoustic environments.