Analysis and perception of sibilant fricatives: Shona data

In addition to the commonly found [s,z] and [∫ȝ], the Shona language has a third pair of sibilants [s,zw w] usually described as labialized alveolar fricatives and sometimes called “whistling” fricatives. Analysis of all these sibilants revealed that the location of the main frequency peak was typically 3 Bark higher for [s,z] than for the remaining four fricatives which did not differ significantly in this respect. Durational differences were slight throughout, and seemed unlikely to contribute as place cues. A likelier possibility for cueing the place distinction, we hypothesized, was an interaction of peak location with the gradient of the high- and low-frequency slopes adjacent to the peak, together perhaps with contributions from the VCV transitions. Experimental manipulation of these variables in synthetic versions of the three voiceless sibilants yielded listener identifications suggesting that (1) a flat HF slope cued [s] overridingly, irrespective of the peak location, but (2) peak location became important when a falling HF slope is used; and (3) a steep LF slope failed to create enough of a “whistling” percept as to outweigh transitional cues to the [∫]−[sw] distinction.