The Closer, The Better: How does voice similarity affect our preference for synthetic voices?

This paper investigates the impact of voice similarity on synthetic voice preference and Quality of Experience (QoE), focusing on two key prosodic features: long-term fundamental frequency (LTF0) or characteristic pitch and speech rate (SR). By conducting subjective tests on synthetic voices with varying degrees of similarity to each participant’s own voice, the study aims to uncover whether and how voice similarity influences synthetic voice preference. Thirty-four participants were recorded reading 10 phonetically balanced Harvard sentences. From these data, we extracted LTF0 using CREPE and SR using Wav2Vec-XLSR-53 . The same features were extracted from four commercial Google TTS voices. The LTF0 and SR of the TTS voices were then matched with the voices of each participant. In addition to the matched voices, four variations were made for LTF0, while two speed variations were made for SR. Personalised listening tests were prepared and administered to each participant, comparing the matched stimulus with a variation in random order. The results show that the participants preferred the matched stimuli in most cases. In particular, this preference was stronger when voice matching was applied to female TTS voices. For male TTS voices, lower LTF0 was preferred. Moreover, matched and faster SR were preferred over slower SR. These findings suggest that voice adaptation and personalisation can enhance perceived QoE in terms of user preference.