The obligatory use of vowel duration in speaking rate normalization

Abstract

Speech segment duration varies with speaking rate and phonetic identity. This study explored how listeners normalize for speaking rate when variation in segmental duration was a result of phonetic identity. Listeners identified the initial consonant in series that ranged from ‘‘beat’’ to ‘‘wheat’’ and ‘‘bead’’ to ‘‘weed.’’ Even though the endpoints of the series were spoken at the same speaking rate, the vowel duration in ‘‘bead’’–‘‘weed’’ was longer than ‘‘beat’’–‘‘wheat.’’ Luce and Charles-Luce [J. Acoust. Soc. Am. 78, 1949–1957 (1985)] showed that vowel duration is an acoustic correlate of final stop voicing. Even though the vowel duration difference was an acoustic correlate of the final consonant voicing, listeners responded to the series as if vowel duration variation were also a cue to speaking rate. Listeners gave more /b/ responses to the ‘‘bead’’–‘‘weed’’ series. These data are inconsistent with models of perception in which acoustic correlates are uniquely assigned to sources in speech production. Instead, speaking rate normalization appears to be an early, autonomous process and the perceptual utilization of duration information for multiple aspects of speech perception may be obligatory. [Work supported by NIDCD Grant No. RO1DCOO219 to SUNY at Buffalo.]