title: A role for amplitude modulation phase relationships in speech rhythm perception.
abstract: Prosodic rhythm in speech [the alternation of "Strong" (S) and "weak" (w) syllables] is cued, among others, by slow rates of amplitude modulation (AM) within the speech envelope. However, it is unclear exactly which envelope modulation rates and statistics are the most important for the rhythm percept. Here, the hypothesis that the phase relationship between "Stress" rate (∼2 Hz) and "Syllable" rate (∼4 Hz) AMs provides a perceptual cue for speech rhythm is tested. In a rhythm judgment task, adult listeners identified AM tone-vocoded nursery rhyme sentences that carried either trochaic (S-w) or iambic patterning (w-S). Manipulation of listeners' rhythm perception was attempted by parametrically phase-shifting the Stress AM and Syllable AM in the vocoder. It was expected that a 1π radian phase-shift (half a cycle) would reverse the perceived rhythm pattern (i.e., trochaic → iambic) whereas a 2π radian shift (full cycle) would retain the perceived rhythm pattern (i.e., trochaic → trochaic). The results confirmed these predictions. Listeners judgments of rhythm systematically followed Stress-Syllable AM phase-shifts, but were unaffected by phase-shifts between the Syllable AM and the Sub-beat AM (∼14 Hz) in a control condition. It is concluded that the Stress-Syllable AM phase relationship is an envelope-based modulation statistic that supports speech rhythm perception.
authors.affiliation: Centre for Neuroscience in Education, Department of Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, United Kingdom.
authors.forename: Victoria
authors.initials: V
authors.lastname: Leong
authors.affiliation: Auditory Perception Group, Department of Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, United Kingdom.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Stone
authors.affiliation: Computational and Biological Learning Lab, Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, United Kingdom.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Turner
authors.affiliation: Centre for Neuroscience in Education, Department of Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, United Kingdom.
authors.forename: Usha
authors.initials: U
authors.lastname: Goswami
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001302:Audiometry, Speech; D003463:Cues; D005260:Female; D006801:Humans; D007600:Judgment; D008297:Male; D010507:Periodicity; D010700:Phonetics; D011897:Random Allocation; D013018:Sound Spectrography; D013067:Speech Perception; D013997:Time Factors; D014833:Voice Quality; D055815:Young Adult