The role of perception in defining tonal targets and their alignment
Abstract (Summary)Tonal targets can be defined in terms of two-dimensions, i.e., "alignment" and "scaling", where alignment specifies the exact temporal implementation of tonal highs (H) and lows (L) relative to structural elements (such as syllables and morae) and their segments. Align¬ment patterns might be constrained by various linguistic factors, such as phonological as well as phonetic factors. Among the phonological factors, the grammar of stress-accent languages specifies that the tones of a pitch accent must be aligned with those syllables that are marked as stressed in the lexicon. Among the phonetic constraints, one finds facts about the perception of pitch and time, both for speech and for non-speech stimuli.This thesis investigates the role of alignment in determining tonal target perception for yes/no question and (narrow focus) statement contours in Neapolitan Italian. These contours are characterized by a melodic rise-fall, analyzed here as a sequence of a LH pitch accent plus a HL phrase tone. The separation of the rise and the fall is clear in the case of long focus constituents containing at least two words with independently stressed syllables. In more typical cases, however, this configuration is acoustically realized as a sequence of three tonal targets, LHL, due to "merging" of the H tone sequence in nuclear position. This thesis shows that the precise alignment of each of those tonal events influences the perception of the question/statement contrast.A read speech corpora, produced by two speakers of Neapolitan Italian, was first ana¬lyzed to acoustically characterize tonal targets in both yes/no questions and narrow focus statements, with target words differing in syllable structure and segmental environment. Later, a set of resynthesized stimuli was created, which constituted the basis for the percep¬tion experiments. Results show that, when tonal targets for the entire rise-fall are displaced later in time, more questions are identified. Also, the sole alignment modification of the first or the second L determines different question responses. The results also suggest that f0 height has a minor role in signaling pitch accent differences, while rise and fall slope have no impact.Additionally, when the shape of the peak in the rise-fall is modified, so that a high plateau is created, more questions are perceived. This phenomenon cannot be accounted for in terms of a parsing difference between the question and the statement phonological tone structures, since those structures are the same. Moreover, the effect was also found for non-native listeners. Namely, American English listeners showed an effect of peak shape, as well as a similar use of the alignment contrast as a consequence of alignment modifications, when identifying questions vs. statements of Neapolitan. This result suggests a universal use of alignment and a psychoacoustic effect of perceived target displacement due to peak shape. Hence, despite acoustic and pragmatic differences between their rise-fall contrasts, American and Neapolitan listeners appear to employ similar perceptual strategies.The Neapolitan results also show that syllable structure manipulations are not able to shift the categorical boundary location between a perceived question and a statement. This result suggests that no look-ahead mechanism is employed when computing perceived tar¬get location. On the other hand, a category boundary shift was found when stimuli were resynthesized from either a question base or a declarative base utterance. This suggests that cues other than target alignment are employed when computing perceived pitch accent contrast. In sum, this thesis proposes that temporal alignment, both as a production and a perception mechanism, must shape phonological systems of intonational contrast, both within and across languages.
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Date of Publication:01/01/2000