Cochlear implant and an operating method thereof

A method for generating an electrical stimulus of a specified intensity on any audio frequency range relating to at least one electrode of a plurality of an implanted electrode array of a cochlear implant, the method comprising

• determining a total signal level of an incoming acoustic signal;
• determining, in accordance with the determined total signal level, an intermediate knee point in a mapping function for one or more frequency bands, wherein the mapping function outputs a charge amount corresponding to a signal level inputted to the mapping function;
• generating a plurality of band limited audio signals in dependence upon the incoming acoustic signal, each band limited acoustic signal representing an associated audio frequency range relating to at least one of a plurality of electrodes of an implantable electrode array of the cochlear implant;
• directly map one or more generated band limited audio signals into a stream of target charge amounts by inputting the signal levels of each of the one or more generated band limited audio signals to the mapping function including the intermediate knee point determined for the corresponding frequency range, and obtaining the corresponding charge amounts outputted by the mapping function as the target charge amounts, and
• delivering electrical stimulation signals to the plurality of electrodes of the implantable electrode array by generating electric charge pulses corresponding to the stream of target charge amounts which are outputted by the mapping function in response to the inputted signal levels of the one or more generated band limited audio signals that are directly mapped,
• wherein the intermediate knee point defines within the mapping function a loudness growth function comprising a first loudness growth function comprising a first incremental gain below the intermediate knee point and a second loudness growth function comprising a second incremental gain above the intermediate knee point, the first incremental gain being higher than the second incremental gain, and
• wherein the mapping function maps the one or more generated band limited audio signals in units of decibels of sound pressure level (dB SPL) into the stream of target charge amounts defined as a percentage of a maximum comfort charge.