Spectral dynamics of sibilant fricatives are contrastive and language specific.

Previous research has extensively investigated the spectral properties of sibilant fricatives with little consideration to how these properties vary over time. To investigate such spectro-temporal variation, productions of English /s/ and /ʃ/ and of Japanese /s/ and /ɕ/ in word-initial, prevocalic position were elicited from adult native speakers. The spectral dynamics of these productions were analyzed in terms of a psychoacoustic measure of peak frequency: "peak ERBN number." Peak ERBN number was computed at 17 evenly spaced points across each fricative production. The resulting peak ERBN number trajectories were analyzed with orthogonal polynomial growth-curve models, to determine how peak frequency varied temporally within each fricative. Three analyses compared (1) the English sibilants to each other, (2) the Japanese sibilants to each other, and (3) English /s/ to Japanese /s/. The results indicated that, in both English and Japanese, the sibilant fricatives differ acoustically in terms of both static (i.e., overall level) and dynamic (i.e., shape) aspects of the peak ERBN number trajectories. Furthermore, English /s/ and Japanese /s/ exhibited language-specific differences in the shape, but not overall level, of peak ERBN number trajectories.