The phonetics of stress clash in spontaneous speech

Abstract

This study examines the rhythm rule (RR) in spontaneous speech to determine its acoustic correlates and phonetic robustness in conversational intonation. RR in English is a phonological process that accommodates stress clash. It has been primarily investigated in controlled speech. Both analyses of RR were considered in this study: (1) accent reversal—the relative prominence of key syllables is reversed, (2) accent deletion—the relative prominence of key syllables is neutralized. Two hypotheses were investigated: (1) RR is always indicated by measurable acoustic properties. (2) RR is subject to intonational factors and depends upon the attraction of a pitch accent for realization. Duration, f0, and amplitude were measured on relevant syllables. ToBI labeling was used to indicate pitch accents and phrase boundaries. Duration was the most consistent acoustic cue to stress clash resolution. When the target phrase attracted a pitch accent, duration indicated stress clash resolution by accent reversal. When the target phrase did not attract a pitch accent, f0 and duration indicated accent deletion. Crucially, when the phrases did not attract pitch accents (were not intonationally prominent), stress clash was resolved. This finding provides support for hypothesis (1): RR is pervasive in the acoustic signal independently of intonational factors.