Comparing Effects of Frequency Maps on Sentence Perception Between Simulated Bimodal and Electric Acoustic Stimulation Hearing

Speech understanding with a cochlear implant (CI) and hearing aid (HA) on either the opposite ear (i.e., bimodal) or the same ear (i.e., EAS) produces a considerable synergistic effect. While many bimodal and EAS users experience significant benefit, others gain little or no benefit or experience interference. One potential contributor to this variability is that the effect of different degrees of residual hearing thresholds in HA ears on the maps has not been seriously considered. Another challenging aspect of previous bimodal and EAS studies is the difficulty of precisely interpreting the results due to different testing, audiologic components, demographic variables, bandwidths, filtering cutoff frequencies, and slopes for either HA or CI ear. Each of these factors precludes controlled comparisons in real bimodal and EAS patients. Existing bimodal and electric acoustic stimulation (EAS) studies suggest highly mixed results regarding frequency fitting maps. This study evaluated various frequency maps on the benefit of bimodal and EAS hearing in sentence perception using acoustic simulation. Results indicated that the optimal map was similar across bimodal and EAS hearing configurations but was influenced by the upper-frequency bounds of residual hearing in the acoustic ear. Results also showed that bimodal and EAS benefit in sentence perception is also similar regardless of signal-to-noise ratio (SNR). In this study, using simulations of bimodal and EAS hearing with normal hearing (NH) listeners, we determined the optimal frequency maps, based on sentence perception scores by adjusting acoustic and electric boundary frequencies.