A speech processor with lateral inhibition for an eight channel cochlea implant and its evaluation by subject testing

To design an optimal signal processor for an eight channel cochlea implant, stimulus current distributions were obtained inside and outside the cochlea removed from a human cadaver. A speech processor including the function of lateral inhibition was proposed to compensate for the wide current spread. The role of the function was evaluated based on the subject testing with respects to the discrimination of synthetic vowels and the loudness estimation of complex tones. From the experimental results, lateral inhibition was proved to be effective to avoide excess current, however, the role of inhibition was not so clear in the discrimination of vowels except /i/ and /e/ in which there were two seperate peaks corresponding to F1 and F2.