Band-specific temporal periodicity enhancement for Cantonese tone perception with noise-excited vocoder

This paper describes a study on the effectiveness of expanding the temporal envelope and periodicity component (TEPC) for Cantonese tone perception. The ultimate goal is to develop speech processing techniques that can improve speech perception of hearing prosthesis users. Cantonese is a popular Chinese dialect with a complex lexical tone system. TEPCs are extracted from a few predefined frequency bands. A nonlinear expansion method is applied to increase the modulation depth of the TEPCs, in order to make the temporal periodicity information more salient. To simulate the speech processing procedures of a cochlear implant, the TEPC is used to modulate a noise carrier. Psychophysical listening tests on Cantonese lexical tone identification are carried out with expanded and unexpanded TEPCs. The experimental results show that: (1) expansion of TEPC from high-frequency band leads to noticeable improvement on tone identification accuracy; (2) the effectiveness of TEPC expansion is more significant for female voice than male voice; (3) the presence of noise carrier in low-frequency band negatively affects tone identification accuracy.