In this paper we present the conception and the implementation of a speech processing interface for auditory prosthesis. This module is based on a numerical speech processing algorithm which modelizes the infected ear and generates the stimulus signals for the cilia cells. This interface uses a gammachirp filter bank (G.F.B) constituted of 16 band pass filters based on IIR filters. The excited electrodes and stimulus signals are selected after a spectral energy analysis of each band. The energy and the amplitude of the most significant impulse responses of the G.F.B outputs are quantized, coded and transmitted to the cochlea electrodes. To validate our work, we tested it on vowels, consonants then on several words pronounced by different speakers.