Investigating the use of formant frequencies in listener judgments of speaker size

Abstract

The formant-pattern present in a given vowel sound will be determined by the vocal-tract length (VTL) of the speaker as well as by phoneme-specific information. Although human listeners tend to associate lower formant-frequencies with larger speakers, it is unclear whether they are responding to VTL information in speech sounds, or simply responding to the formant-pattern present in the sound. In this experiment listeners were presented with pairs of synthetic vowels from the set of (/i æ ʊ/), which could differ on the basis of simulated VTL and vowel category, within-pair. Listeners were divided into groups based on the number of formants contained by stimulus vowels (2, 3, 4, and 5-formant vowel groups). For each trial, listeners were asked to indicate which vowel sounded like it had been produced by a taller speaker. Results indicate that listeners do not rely solely on VTL cues when making speaker-size judgments, and that they exhibit biases towards selecting given phonemes as taller, even when contrary to the VTL differences between the voices. Furthermore, the higher formants (up to F5) are used by listeners when making speaker-size judgments, though not in a manner consistent with VTL-based speaker-size judgments.