Expression of Speaker's Intentions through Sentence-Final Particle/Intonation Combinations in Japanese Conversational Speech Synthesis

Aiming to provide the synthetic speech with the ability to express speaker's intentions and subtle nuances, we investigated the relationship between the speaker's intentions that the listener perceived and sentence-final particle/intonation combinations in Japanese conversational speech. First, we classified F0 contours of sentence-final syllables in actual speech and found various distinctive contours, namely, not only simple rising and falling ones but also rise-and-fall and fall-and-rise ones. Next, we conducted subjective evaluations to clarify what kind of intentions the listeners perceived depending on the sentence-final particle/intonation combinations. Results showed that adequate sentence-final particle/intonation combinations should be used to convey the intention to the listeners precisely. Whether the sentence was positive or negative also affected the listeners' perception. For example, a sentence-final particle 'yo' with a falling intonation conveyed the intention of an "order" in a positive sentence but "blame" in a negative sentence. Furthermore, it was found that some specific nuances could be added to some major intentions by subtle differences in intonation. The different intentions and nuances could be conveyed just by controlling the sentence-final intonation in synthetic speech.