The importance of phase in the perception of intervocalic stop consonants

Abstract

Identification experiments were performed to assess the relative importance of phase information versus amplitude information of vowel–stop–consonant–vowel (VCV) utterances for intervocalic consonant perception. Three types of stimuli were constructed from the VCVs spoken by six German speakers: (1) swapped stimuli: synthesized from the phase spectrum of one VCV utterance and the amplitude spectrum of another; (2) amplitude-only stimuli: the original amplitude spectrum of a VCV utterance combined with a zero or random phase spectrum; (3) phase-only stimuli: original phase spectrum with zero or random amplitude spectrum. About 66% of intervocalic stop consonants in the phase-only stimuli could be correctly identified as compared to less than 25% for amplitude-only stimuli. Over 55% of type 1 stimuli were identified as the VCV utterances that had provided the phase information, and less than 22% as those that had provided the amplitude information. Consonant identification performance was seen to vary with voicing and place of articulation of the stops, as well as with vowel context. The results indicated that it was the phase spectrum, rather than the amplitude spectrum of a VCV utterance that conveys more important information for stop consonant perception.