Doctor of Philosophy, The Ohio State University, 2015, Linguistics

Voiceless sibilant fricatives, such as the consonant sounds at the beginning of the English words sea and she, are articulated by forming a narrow constriction between the tongue and the palate, which directs a turbulent jet of air toward the incisors downstream. Thus, the production of these sounds involves the movement of a number of articulators, including the tongue, jaw, and lips; however, the principal method for analyzing the acoustics of sibilant fricatives has been to extract a single “steady state” interval from near its temporal midpoint, and estimate spectral properties of this interval. Consequently, temporal variation in the spectral properties of sibilant fricatives has not been systematically studied. This dissertation investigated the temporal variation of a single spectral property that denotes the most prominent psychoacoustic frequency, i.e. peak ERB-number. The dynamic aspects of peak ERB-number trajectories were analyzed with fifth-order polynomial time growth curve models. A series of analyses revealed a number of novel findings A comparison of English- and Japanese-speaking adults indicated that both language-internal sibilant contrasts are indicated by dynamic properties of peak ERB-number across the time course of the sibilants. A cross-linguistic comparison indicated that the peak ERB-number of a sibilant follows a language-specific trajectory. Next, the development of the sibilant contrast in native English- and Japanese- acquiring children was investigated in terms of peak ERB-number trajectory. The English-acquiring children contrasted the sibilants in terms of similar aspects of peak ERB-number trajectory as the English-speaking adults. Moreover, the extent to which the children differentiated the sibilants increased with age. The analysis of the Japanese-acquiring children was complicated by an apparent developmental regression in the five-year-olds. Effects of vowel context on peak ERB-number trajectory were examined i (open full item for complete abstract)

Committee: Mary Beckman (Advisor); Micha Elsner (Committee Member); Eric Fosler-Lussier (Committee Member); Eric Healy (Committee Member) Subjects: Linguistics

Doctor of Philosophy, The Ohio State University, 2015, Linguistics

Phonetic reduction is a common feature of everyday speech. Numerous studies have documented that words, syllables, and other linguistic elements which are more predictable are pronounced with less acoustic prominence than words, syllables, and elements which are less predictable. This phenomenon is referred to as predictability-based phonetic reduction. Several accounts of this phenomenon exist. The focus of this dissertation is the listener-oriented account, which theorizes that predictability-based phonetic reduction arises from an interaction between the competing forces of conservation of effort and conservation of intelligibility. From this perspective, talkers use the least effort possible to provide the maximum level of comprehension---that is, their speech productions are guided by consideration of the listener's needs. For elements which are predictable, likelihood of comprehension is relatively high, and thus the talker is free to conserve effort and produce the element in a phonetically reduced way. For unpredictable elements, however, likelihood of comprehension is relatively low, and thus the talker must produce the element in a clear manner. This dissertation presents the results of nine experiments examining different aspects of the listener-oriented account. The first three experiments tested the prediction of this account that individual theory of mind ability is positively correlated with extent of phonetic reduction. Results suggest that no such relationship exists for the variables of lexical frequency, phonological neighborhood density, and second mention reduction. For semantic predictability, however, a negative correlation was observed, such that talkers with poor theory of mind ability had a greater extent of phonetic reduction than talkers with good theory of mind ability. These results fail to support the listener-oriented prediction. The next three experiments tested the foundational assumption of the listener-oriented account th (open full item for complete abstract)

Committee: Cynthia Clopper (Advisor); Mary Beckman (Committee Member); Rebecca Morley (Committee Member); Shari Speer (Committee Member) Subjects: Linguistics