A STUDY ON COCHLEAR IMPLANT SYSTEM BASED ON A PHYSIOLOGICAL MODEL OF THE PERIPHERAL AUDITORY SYSTEM

点击翻译按钮获取中文摘要

The purpose of this study is inverse processing of the peripheral auditory model and multi-pulse coding fro the cochlear implant. We proposed a recursive algorithm that approximates the input signal only from the positive part of the wave. Reverse conversion of the nonlinear saturation characteristic in cochlea was realized by solving a reverse problem about a nerve transfer substance on the basis of Meddis's nerve tranducion model. It also reexamined that an oscillation might occur in instability of the reversing AGC (automatic gain control) by Slaney for large inputs. Although the precision was high to small signals also in the Meddis's model, it became unstable to large inputs. Since it processed as a linear system, the transfer characteristic of the sound system which results in an inner ear from an outside ear was realized despite reverse conversion being inadequate.The efficient multi-channel pulsation algorithm based on the principle of the voice coding for efficient conversion to the cochlear implant electrode stimulation pulses was developed. By the voice coding method, analyzing an input sound and having obtained the approzimation filter, on this problem it searches for the optimum combination series about a given filter set. The pulse series of the positive/negative which makes a filter set a mark is obtained as compression voice information, and matches this with the electrode pulse. When accuracy of coding was checked by coding decoding, it was found that the high frequency components with small energy falls out and runs short in analysis process relatively compared with that of low frequency. Although the effect accepted when high frequency enhancement and spectrum flattening processing were incorporated, it was inadequate in respect of the tone-quality improvement. Although the unsolved problem had remained, the possibility of this system was checked as a quality voice coding for the cochlear implantation.