Cochlear implant simulator with independent representation of the full spiral ganglion.

In cochlear implant simulation with vocoders, narrow-band carriers deliver the envelopes from each analysis band to the cochlear positions of the simulated electrodes. However, this approach does not faithfully represent the continuous nature of the spiral ganglion. The proposed "SPIRAL" vocoder simulates current spread by mixing all envelopes across many tonal carriers. SPIRAL demonstrated that the classic finding of reduced speech-intelligibility benefit with additional electrodes could be due to current spread. SPIRAL produced lower speech reception thresholds than an equivalent noise vocoder. These thresholds are stable for between 20 and 160 carriers.