Perception of Brief Stimuli that Resemble Rapid Formant Transitions

Abstract

One problem for the child who is acquiring language is the lack of acoustic similarity between the formant transitions of an initial stop, and the formant transitions of the postvocalic unreleased allo-phone of the same stop. Brief two-component stimuli were used to study perceptual similarity among members of a set of synthetic sounds which approximate the mirror-image formant transitions for /b d g/ in prevocalic and postvocalic positions. The two components of a stimulus were 40-msec tone bursts having linear frequency glissandos with frequency motions approximating the first and second or second and third formant patterns. Results indicate that there is no inherent similarity between mirror-image glissando patterns. Judgments of relative perceptual similarity were based on the glissando component corresponding in frequency to the second formant, even when this component was significantly reduced in amplitude relative to the other component. While the perceptual importance of the second formant in speech is well known, it is difficult to account for these results in terms of basic psychophysical data on frequency discrimination, loudness, or masking. These results, and the observation that some mirror-image responses for /g/-like transitions occur under certain special conditions argue for the presence of frequency change detectors that may play an important role in speech perception. [Research supported in part by NIH grants.]