Simulations of High-Frequency Vocoder on Mandarin Speech Recognition for Acoustic Hearing Preserved Cochlear Implant

Vocoder simulations are generally adopted to simulate the electrical hearing induced by the cochlear implant (CI). Our research group is developing a new four-electrode CI microsystem which induces high-frequency electrical hearing while preserving low-frequency acoustic hearing. To simulate the functionality of this CI, a previously developed hearing-impaired (HI) hearing model is combined with a 4-channel vocoder in this paper to respectively mimic the perceived acoustic hearing and electrical hearing. Psychoacoustic experiments are conducted on Mandarin speech recognition for determining parameters of electrodes for this CI. Simulation results show that initial consonants of Mandarin are more difficult to recognize than final vowels of Mandarin via acoustic hearing of HI patients. After electrical hearing being induced through logarithmicfrequency distributed electrodes, speech intelligibility of HI patients is boosted for all Mandarin phonemes, especially for initial consonants. Similar results are consistently observed in clean and noisy test conditions.