Voice Disguise vs. Impersonation: Acoustic and Perceptual Measurements of Vocal Flexibility in Non Experts

The aim of this study is to assess the potential for deliberately changing one's voice as a means to conceal or falsify identity, comparing acoustic and perceptual measurements of carefully controlled speech productions. Twenty-two non expert speakers read a phoneticallybalanced text 5 times in various conditions including natural speech, free vocal disguise (2 disguises per speaker), impersonation of a common target for all speakers, impersonation of one specific target per speaker. Long-term average spectra (LTAS) were computed for each reading and multiple pairwise comparisons were performed using the SDDD dissimilarity index. The acoustic analysis showed that all speakers were able to deliberately change their voice beyond self-typical natural variation, whether in attempting to simply disguise their identity or to impersonate a specific target. Although the magnitude of the acoustic changes was comparable in disguise vs. impersonation, overall it was limited in that it did not achieved between-speaker variation levels. Perceptual judgements performed on the same material revealed that naive listeners were better at discriminating between impersonators and targets than at simply detecting voice disguise.