Assessing the quality of voice synthesizers

We address the voice quality assessment by focusing on the harmonic and temporal aspects that are less treated in the literature. The main focus is on the influence on synthetic voice quality of the higher formants. We view the higher formants role as primarily mediated by the ratios of their frequencies and that of the pitch. We present a comparative study between human and synthetic voice in this respect. The presented analysis involves, beyond the determinations of the fundamental frequency and formants, the determination of the durations of vowels. Recognizing that a single quality criterion could not give a sufficient understanding of the voice quality process, we suggest a set of criteria regarding the discussed aspects of the voice and introduce a set of parameters to characterize the quality.