What Determines Personality Impressions of Synthetic and Natural Voices? The Effects of Voice Quality and Intonation

The present study investigated how acoustic and phonetic characteristics of synthetic and natural voices affect personality impressions of the voices. To this end, we conducted a personality rating experiment in which 30 native Korean speakers judged the perceived personality of natural Korean utterances and their synthetic counterparts (voice clones) using the Big-Five personality model. Various acoustic parameters, including measures of voice quality, F0, and articulation rate, were then extracted from the speech, and Intonational Phrase boundary tones were annotated. The ratings of the Big-Five personality traits were reduced to two dimensions (P1: agreeableness, conscientiousness, and emotional stability; P2: extraversion and openness) using a principal component analysis. The results suggest that the acoustic differences between state-of-the-art synthetic speech and its original counterpart can produce varying effects on personality perception. For example, speech produced with a narrower F0 range received lower scores on P1 and P2, but for male speakers, this effect was only observed in synthetic voices, likely due to the less-natural intonational patterns used. The intonation analysis further demonstrates that across speech type, using context-appropriate tones or those conveying positive attitudes improves the overall impression of the voice (both P1 and P2). The results also suggest that a less-modal voice enhances the personality scores overall, but specific voice qualities (i.e., breathiness and creakiness) and voice pitch seem to affect P1 and P2 differently. The present study demonstrates a range of acoustic and phonetic characteristics that should be considered when designing personas for AI voices or developing more likable synthetic voices.