Identification of musical instruments by normal-hearing subjects listening through a cochlear-implant simulation

Signal processing in a cochlear implant (CI) is primarily designed to convey speech and environmental sounds, and can cause distortion of musical timbre. Systematic investigation of musical instrument identification through a CI has not yet revealed how timbre is affected by the implant’s processing. In this experiment, the bandpass filtering, rectification, and low-pass filtering of an implant are simulated in matlab. Synthesized signals representing 12 common instruments, each performing a major scale, are processed by simulations using up to 8 analysis channels. The unprocessed recordings, together with the 8 simulation conditions for 12 instruments, are presented in random order to each of the subjects. The subject’s task is to identify the instrument represented by each item. The subjects also subjectively score each item based on similarity and pleasantness. We anticipate performance using the simulation will be worse than the unprocessed condition because of the limited information delivered by the envelopes of the analysis channels. These results will be analyzed as a confusion matrix and provide a basis for contrasting the information used by subjects listening to the unprocessed and processed materials. Understanding these differences should aid in the development of new processing strategies to better represent music for cochlear implant users.