A new approach for speech synthesis in cochlear implant systems based on electrophysiological factors

Speech synthesis models have been considered as viable tools for performance evaluation of cochlear stimulation algorithms, due to the difficulties of clinical tests.

The present study has developed a tool that can be used before any audio signal reconstruction algorithm, which shows more conformity with the electrophysiological parameters of the patient in evaluation of the cochlear implant stimulation algorithms.

In this method, excitable nerve fiber characteristics such as stimulation threshold and effective refractory period have been considered in the signal pre-reconstruction process. This algorithm subsumes the user's biological parameters (e.g., the manner of distribution of the remaining intact nerve fibers) as well as the stimulation signal parameters (e.g., stimulation rate, pulse width, amplitude of stimulation, the distance between stimulation electrode and fibers) in the signal pre-reconstruction.

Effect of changes in these parameters can be observed by the number of excited fibers, which is directly related to the signal intensity and pitch frequency perceived by the user. The obtained results from simulations are in accordance with previous clinical findings. Also, the ability of the proposed tool can be seen by the correspondence between the results obtained from the proposed model and the amplitude growth functions of the cochlear implant users.

This paper has introduced a tool for signal reconstruction from electrical stimulation so that a more comprehensive criterion for examination of the stimulating algorithms in cochlear implant can be achieved.