An Improved Strategy Based On The Auditory-perception-wavelet-Package For Chinese Tone Perception In Cochlear Implant

Cochlear implant (CI) is a medical device that can restore the residual auditoryperception for the profoundly or totally deafened person via functional electricalstimulation. At present, however，the speech coding strategies for Chinese tone still havesome shortcomings, such as poor perception of tone, melodies and music.According to the patients’ lack of tone perception, based on the decisive role ofinformation retrieval to tone perception in both time domain and frequency domain, wepropose the wavelet packet decomposition strategy using multi-resolution analysis andnon-uniformity dividing time-frequency space technology. To effectively accesstime-frequency information in order to improve the patients’ tone pitch perception andspeech quality.On the account of the limited number of cochlear implant electrode, basing onensuring the complete information obtained from the time-frequency domain andpreventing the multi-electrode channel mutual interference, we apply the channelmaximum energy criterion for selection of the effective channels so as to remove thechannels containing the less information of speech, which is to ensure the transmission ofeffective information and to avoid interference between the electrode channels.On account of the noise masking interference of Chinese tones causing by thehigh-speed pulse modulation, we propose the modulation depth options which greatlyweak the interference of in-band noise and thus improve the access to Chinese tones.The results show that the combination of wavelet packet decomposition basing onauditory perception and depth of modulation can effectively suppress the in-band noiseand enhance the tone perception.