Minoru TSUZAKI, Hiroaki KATO and Masako TANAKA
Shrinkage in the Perceived Duration of Speech and Tone by Acoustic Replacement
Abstract:To investigate mechanisms for perceiving the duration of an auditory event, an effect of perceptual grouping upon perceived durations was studied psychophysically. In the first experiment, the perceived duration of a spoken word was measured under three conditions of acoustic continuity, i.e., (a) intact, (b) noise-replaced, and (c) gap-replaced, as a function of the duration of the target stimulus. Under the noise-replaced condition, a portion of the target stimulus was physically replaced with a noise burst. Under the gap-replaced condition, the replacement was made with a gap. The gap-replacement resulted in a prominent shrinkage of the perceived duration. In the case of noise-replacement, the amount of shrinkage was moderate but highly significant, although the word employed was perceived to be phonetically intact. Independent of this effect of replacement, the amount of shrinkage was affected by the physical duration of the target stimulus. The second experiment tested an effect of noise replacement on the perceived duration of a tone burst. In this case, the noise replacement also shrunk the perceived duration of the non-speech stimulus. This noise-induced shrinkage could be regarded as having occurred at a stage of auditory signal processing that functions for a wide range of acoustic stimuli. The phenomenon is discussed in relation to a revised model for perceived durations.