Wearable digital speech processor for cochlear implants using a TMS320C25

Based on a single-chip DSP (TMS320C25, Texas Instruments) a programmable battery-operated sound processor with a digital encoder interface for the Nucleus-22 cochlear implant (CI) was built. The number of quasi-simultaneously addressed electrodes is only limited by the selected pulse width and the maximum rate of stimulation and can be as high as 10 electrodes at 300 Hz repetition rate. Implementation of various processing strategies (formant or channel vocoder, filterbank, zero crossings, etc.) is possible as well as sophisticated adaptive noise reduction. Programs and stimulation parameters are stored in electrically erasable memory and may be updated via a host computer. The built-in analog output may be used for single-channel stimulation or acoustic verifications of the sound processing algorithms. The power consumption with current 16K word data memory and at maximum stimulation rate is about 1 Watt, which necessitates recharging of batteries after 11 h.