Modification of harmonic peak-to-valley ratio for controlling roughness in voice conversion

A method for modifying voice quality attributes, i.e. breathiness and roughness, is presented in the context of voice conversion. Both breathiness and roughness of a speaker are collectively modelled by harmonic peak-to-valley ratio (HPVR) in the speaker´s speech spectrum. The average HPVR is modified through a post-filtering operation after the conversion of spectral envelope, pitch and other speaker individuality features. It is shown that average HPVR for various speakers correlates well with the perceived breathiness and roughness in their voices. Further, it is shown through subjective experiments that the proposed modification in HPVR results in improved subjective rating of the transformed speech signal.