Expressive speech synthesis: synthesising ambiguity

Previous work in HCI has shown that ambiguity, normally avoided in interaction design, can contribute to a user’s engagement by increasing interest and uncertainty. In this work, we create and evaluate synthetic utterances where there is a conflict between text content, and the emotion in the voice. We show that: 1) text content measurably alters the negative/positive perception of a spoken utterance, 2) changes in voice quality also produce this effect, 3) when the voice quality and text content are conflicting the result is a synthesised ambiguous utterance. Results were analysed using an evaluation/activation space. Whereas the effect of text content was restricted to the negative/positive dimension (valence), voice quality also had a significant effect on how active or passive the utterance was perceived (activation).