Acoustic Cochlear Implant Models Incorporating Electrical Field Interaction between Neighboring Electrodes

Abstract

Cochlear implant (CI), which has been a com-mercial device for nearly thirty years, can provide opportuni-ties for patients with severe to profound hearing impairment to regain hearing. Sound processed in the CI can be modeled by acoustic CI models on specific stimulating strategies. Speech processed by acoustic CI models was used to test normal hear-ing test subjects and can be a basis to evaluate the perfor-mance of various stimulating strategies. Unfortunately, there is still a significant performance difference between hearing test result based on acoustic CI model with normal hearing test subjects with hearing tests from CI patients. There are a num-ber of explanations for this, but one important factor is that traditional acoustic models do not account for the electric field interaction between electrodes. For CI users, the electrical field interaction or current spread between electrodes distorts the speech and introduce noises. In order to model the electri-cal field interaction in the acoustic model, we proposed a new SPREAD model which is created by the activating function profile generated from a finite element model we developed. In previous SPREAD model, the current spread was fixed at a certain decay rate. In the proposed model, activating function and finite element model of a CI is introduced to improve the SPREAD matrix. The performance of the proposed SPREAD matrix with the acoustic CI model significantly improves its match with clinical CI data. This shows the acoustic CI model with the proposed SPREAD matrix can be a more accurate model to evaluate the performance of CI stimulating strategies.KeywordsCochlear implant (CI)electrical field interac-tionacoustic modelcurrent spreadactivating function