Prosodic Phrasing in Spontaneous Swedish

Abstract: One of the most important functions of prosody is to divide the flow of speech into chunks. The chunking, or prosodic phrasing, of speech plays an important role in both the production and perception of speech. This study represents a move away from the laboratory speech examined in previous, related studies on prosodic phrasing in Swedish, since a spontaneous, Southern Swedish speech material is investigated. The study is, however, not primarily intended as a study of the Southern Swedish dialect; rather Southern Swedish is used as a convenient object on which to test various hypotheses about the phrasing function of prosody in spontaneous speech. The study comprises both analyses of production data and perception experiments, and both the phonetics and phonology of prosodic phrasing is dealt with. First, the distribution of prosodic phrase boundaries in spontaneous speech is examined by considering it as a reflection of optimality theoretic constraints that restrain the production and perception of speech. Secondly, the phonetic realization of prosodic phrase boundaries is investigated in a study on articulation rate changes within the prosodic phrase. Evidence of phrase-final lengthening, a reduction of the articulation rate in the final part of the prosodic phrase, is found. The tonal means used to signal coherence within the prosodic phrase is subsequently investigated. An attempt is made to test the two Lund intonation models’ capacities for describing spontaneous speech. The two approaches have different implications for the amount of preplanning needed, which makes them particularly interesting to compare by testing spontaneous data. The results indicate that no or little preplanning is needed to produce tonally coherent phrases. No evidence is found to suggest e.g. that speakers accommodate for the length of the upcoming phrase by starting longer phrases with a higher F0 than short phrases. An explanation is sought for variation in F0 starting points found in the data despite F0’s insensitivity to phrase length. It is concluded that F0 is used to signal coherence even across prosodic phrase boundaries. It is furthermore found that tonal coherence signals are used to override strong boundary signals in spontaneous speech, thereby making initially unplanned additions possible. Finally, the perception of boundary strength is examined in two perception experiments. Listeners are found to agree well in their perceptual judgments of boundary strength, and it is shown that the main correlate to perceived boundary strength in spontaneous speech is pause length. The useful distinction between weak, prosodic phrase boundaries and strong, prosodic utterance boundaries in descriptions of read speech is found to be inappropriate for descriptions of spontaneous speech. It fails to capture the conflicting local and global signals of boundary strength and coherence that arise when strong boundary signals are overriden by coherence signals. The possibility to use conflicting signals in this way is seen as an important asset to the speaker as it makes changes in the speech plan possible, and it is regarded to be a characteristic of prosodic phrasing in spontaneous speech.