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

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.

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.

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.

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.