Speech processing related changes in the speech spectra may often lead to unwanted changes in the effective degree of voicing, which in turn may degrade the speech quality. This phenomenon is studied more closely in this paper, first on a theoretical level and then in the context of voice conversion. Moreover, a simple but efficient approach for avoiding the unwanted changes in the effective level of voicing is proposed. The usefulness of the proposed voicing level control is demonstrated in a practical voice conversion system. The compensation of the changes in the degree of voicing is found to reduce the average level of noise in the output and to enhance the perceptual speech quality.
Bibliographic reference. Nurminen, Jani / Tian, Jilei / Popa, Victor (2007): "Voicing level control with application in voice conversion", In INTERSPEECH-2007, 1973-1976.