An incremental excitation scale for cochlear implants

A loudness matching procedure was used to construct an excitation scale for cochlear implant patients relating neural excitation to electric charge per pulse. Statistical analysis shows the relationship to be linear for sufficiently low charge levels, with a constant slope across electrodes within individual patients. The excitation scale enables an “incremental” encoding procedure from acoustic level to electric stimulus that is independent of the pulse rate used. The statistical properties of the scale parameters can be used to simplify the fitting procedure for the implant processor. Perception of vowels and consonants using conventional and “incremental” encoding produced similar scores for four patients.