Acoustic correlates of talker sex and individual talker identity are present in a short vowel segment produced in running speech.

Although listeners routinely perceive both the sex and individual identity of talkers from their speech, explanations of these abilities are incomplete. Here, variation in vocal production-related anatomy was assumed to affect vowel acoustics thought to be critical for indexical cueing. Integrating this approach with source-filter theory, patterns of acoustic parameters that should represent sex and identity were identified. Due to sexual dimorphism, the combination of fundamental frequency (F0, reflecting larynx size) and vocal tract length cues (VTL, reflecting body size) was predicted to provide the strongest acoustic correlates of talker sex. Acoustic measures associated with presumed variations in supralaryngeal vocal tract-related anatomy occurring within sex were expected to be prominent in individual talker identity. These predictions were supported by results of analyses of 2500 tokens of the /epsilon/ phoneme, extracted from the naturally produced speech of 125 subjects. Classification by talker sex was virtually perfect when F0 and VTL were used together, whereas talker classification depended primarily on the various acoustic parameters associated with vocal-tract filtering.