![]() Depending on the insertion depth and extent of the electrode array, the input acoustic frequency may be lower than the characteristic frequency associated with the electrode position, resulting in tonotopic mismatch. Especially for bimodal listeners, the acoustic-to-electric frequency allocation typically maximizes the amount of acoustic information within the CI. For EAS patients, the low input frequency to the CI is often adjacent to the extent of acoustic hearing. For bimodal patients, clinical fitting of the CI is often performed without regard to the extent of residual acoustic hearing. For bimodal listeners, there is no peripheral interaction between acoustic and electric hearing, which may be advantageous. ![]() ![]() For EAS patients, the current spread associated with electric stimulation may interfere with acoustic hearing at the periphery. With bimodal hearing, electric hearing via CI is combined with acoustic hearing in the contralateral ear. With electric-acoustic stimulation (EAS), electric hearing via CI is combined with acoustic hearing in the ipsilateral ear several CI manufacturers combine a hearing aid with the CI processor. It is unclear whether acoustic and electric stimulation patterns are best combined within the same ear or across ears. This suggests differences among CI users’ abilities to combine acoustic and electric stimulation patterns 27, 28. However, some CI users do not experience significant benefits with acoustic-electric hearing 22, 23, 24, and others experience interference between acoustic and electric hearing 20, 25, 26. Adding detailed low-frequency information via acoustic hearing (aided or unaided) to electric hearing can benefit CI users’ speech and music perception 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21. The coarse spectral resolution provided by cochlear implants (CIs) greatly limits performance in challenging listening conditions such as perception of speech in noise, speech prosody, vocal emotion, tonal language, music, etc. These simulation results suggest acoustic and electric hearing may be more effectively and efficiently combined within rather than across ears, and that tonotopic mismatch should be minimized to maximize the benefit of acoustic-electric hearing, especially for EAS. IE was significantly better for EAS than for bimodal listening IE was sensitive to tonotopic mismatch for EAS, but not for bimodal listening. Performance was best when acoustic and electric hearing was combined in the same ear. For CI simulations, the output frequency range was 1.2–8.0 kHz to simulate a shallow insertion depth and the input frequency range was varied to provide increasing amounts of speech information and tonotopic mismatch. The input/output frequency range for acoustic hearing was 0.1–0.6 kHz. Vowel recognition was measured in normal-hearing subjects listening to simulations of unimodal, EAS, and bimodal listening. The goal of this study was to evaluate factors that affect IE in EAS and bimodal listening. Integration efficiency (IE the ratio between observed and predicted performance for acoustic-electric hearing) can be used to estimate how well acoustic and electric hearing are combined. Advances in cochlear implant (CI) technology allow for acoustic and electric hearing to be combined within the same ear (electric-acoustic stimulation, or EAS) and/or across ears (bimodal listening).
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