Wavelet Packet Filterbank for Speech Processing Strategies in Cochlear Implants

Current speech processing strategies for cochlear implants use a filterbank which decomposes the audio signals into multiple frequency bands each associated with one electrode. Pitch perception with cochlear implants is related to the number of electrodes inserted in the cochlea and to the rate of stimulation of these electrodes. The filterbank should, therefore, be able to analyze the time-frequency features of the audio signals while also exploiting the time-frequency features of the implant. This study investigates the influence on speech intelligibility in cochlear implant users when filterbanks with different time-frequency resolutions are used. Three filter-banks, based on the structure of a wavelet packet transform but using different basis functions, were designed. The filter-banks were incorporated into a commercial speech processing strategy and were tested on device users in an acute study