Effects of phase on the perception of intervocalic stop consonants1
Identification experiments were performed to assess the relative importance of Fourier phase versus amplitude for intervocalic stop consonant perception. In the first experiment, three types of stimuli were constructed from VCV signals: (1) Swapped stimuli, a swapped stimulus has the amplitude spectra of its consisting segments from one VCV signal and its corresponding phase spectra from another; (2) Phase-only stimuli; and (3) Amplitude-only stimuli. It was shown that the perception of intervocalic stop consonants varies from amplitude dominance to phase dominance as the Fourier analysis window size increases. The crossover lies somewhere between 192ms and 256ms. The influence of phase at smaller window sizes was elaborated in the second experiment. This experiment demonstrated that phonetically different signals can be constructed by combining the same short-time amplitude spectra with different phase spectra, so the short-time amplitude spectra displayed on a spectrogram cannot exclusively specify a stop consonant. In both experiments, the perception of voicing in stops was found to rely strongly on phase information while the perception of the place of articulation was mainly determined by amplitude information.
phase perception stop consonant amplitude voicing place of articulation