Invariant cues for place of articulation in stop consonants.

In a series of experiments, identification responses for place of articulation were obtained for synthetic stop consonants in consonant-vowel syllables with different vowels. The acoustic attributes of the consonants were systematically manipulated, the selection of stimulus characteristics being guided in part by theoretical considerations concerning the expected properties of the sound generated in the vocal tract as place of articulation is varied. Several stimulus series were generated with and without noise bursts at the onset, and with and without formant transitions following consonantal release. Stimuli with transitions only, and with bursts plus transitions, were consistently classified according to place of articulation, whereas stimuli with bursts only and no transitions were not consistently identified. The acoustic attributes of the stimuli were examined to determine whether invariant properties characterized each place of atriculation independent of vowel context. It was determined that the gross shape of the spectrum sampled at the consonantal release showed a distinctive shape for each place of articulation: a prominent midfrequency spectral peak for velars, a diffuse-rising spectrum for alveolars, and a diffuse-falling spectrum for labials. These attributes are evident for stimuli containing transitions only, but are enhanced by the presence of noise bursts at the onset.