The role of the gross spectral shape as a perceptual cue to place articulation in initial stop consonants.

This series of studies explored the extent to which the gross shape of the onset spectrum is used by the listener for the identification of place of articulation in initial stop consonants. Synthetic stimuli were generated with onset frequencies appropriate to the syllables [ba bi du da di du] and with the gross shape of the onset spectrum manipulated to be appropriate for either alveolar consonants or labial consonants. Stimuli were presented for identification and discrimination. In addition, adaptation effects of stimuli containing appropriate frequency and shape and incompatible frequency and shape were explored on a place-of-articulation onset continuum. Although identification performance was determined by onset frequency rather than gross shape of the spectrum, presentation of stimuli in which shape was inconsistent with frequency reduced identification performance. Further, subjects could discriminate stimuli which varied only in spectral shape. Finally, significantly less adaptation was found for a [da] onset with a labial spectrum shape than [da] onset with an alveolar spectrum shape. These results suggest that although the invariant properties residing in the gross shape of the onset spectrum may serve as a classificatory framework for the phonetic dimensions of natural language, they may not provide the primary perceptual attributes for place of articulation in ongoing speech processing.