Timbre perception of cochlear implant users

Abstract

The timbre perception of cochlear implantees (CI) is poor compared to normal hearing (NH) listeners. The cues that are normally transmitted to NH listeners may be less salient or even absent for CI users. From the literature, two spectral (brightness (Tb) and irregularity (IRR)) and two temporal timbre parameters (log rise-time (LRT) and sustain/decay (S/D) parameter (n)) have been identified as important timbre parameters. Each of these parameters was extracted for a set of thirteen instruments. Sounds could be resynthesized according to the specific timbre parameter set. The variation of loudness, pitch and perceived duration as functions of the timbre parameters were investigated to provide systematic balancing methods. The just-noticeable differences (JNDs) were obtained for each of the parameters for thirteen instruments for NH listeners and a reduced instrument set of nine instruments for the CI users using a 1-up, 2-down, two-alternative, forced choice procedure. From the JNDs, predicted confusion matrices were constructed. From the confusion matrices, a feature information transmission analysis (FITA) indicated the salience of each of the parameters and NH and CI results could be compared.