The role of linguistic contrasts in the auditory feedback control of Speech

Thesis (Ph. D. in Speech and Hearing Bioscience and Technology)--Harvard-MIT Division of Health Sciences and Technology, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 165-180).Speakers use auditory feedback to monitor their own speech, ensuring that the intended output matches the observed output. By altering the acoustic feedback signal before it reaches the speaker's ear, we can induce auditory errors: differences between what is expected and what is heard. This dissertation investigates the neural mechanisms responsible for the detection and consequent correction of these auditory errors. Linguistic influences on feedback control were assessed in two experiments employing auditory perturbation. In a behavioral experiment, subjects spoke four-word sentences while the fundamental frequency (FO) of the stressed word was perturbed either upwards or downwards, causing the word to sound more or less stressed. Subjects adapted by altering both the FO and the intensity contrast between stressed and unstressed words, even though intensity remained unperturbed. An integrated model of prosodic control is proposed in which FO and intensity are modulated together to achieve a stress target. In a second experiment, functional magnetic resonance imaging was used to measure neural responses to speech with and without auditory perturbation. Subjects were found to compensate more for formant shifts that resulted in a phonetic category change than for formant shifts that did not, despite the identical magnitudes of the shifts. Furthermore, the extent of neural activation in superior temporal and inferior frontal regions was greater for cross-category than for within-category shifts, evidence that a stronger cortical error signal accompanies a linguistically-relevant acoustic change. Taken together, these results demonstrate that auditory feedback control is sensitive to linguistic contrasts learned through auditory experience.by Caroline A. Niziolek.Ph.D.in Speech and Hearing Bioscience and Technolog

The disciplines of vocal pedagogy: towards a holistic approach

This dissertation comprises an exploration of the thesis that a holistic education entailing multi-disciplinary study is essential if classical singers and vocal pedagogues are to be prepared adequately for performance, for their teaching role, and for cooperation in inter-professional relations. The disciplines pertinent to vocal pedagogy are examined, and their varied contributions are discussed with a view to showing the ways in which they are mutually supportive. The case is argued on the basis of an exhaustive analysis of the relevant literature, and is underpinned by my wide professional experience as a soprano, and as a teacher both in primary, secondary and higher education, and in private practice at home and abroad. Starting with a survey of views on vocal pedagogy from biblical and classical times to the present day, important diverse roots are exposed, yielding differing and even conflicting tonal ideals which have a bearing on the consideration of different singing styles, and the interpretation of songs and arias. Ethics and psychology are identified as central to the entire pedagogical process, along with the scientific basis of singing, encompassing acoustics, anatomy and physiology, with special reference to the bearing of the latter two upon vocal health and hygiene. A detailed consideration of singing technique is the centrepiece of the dissertation, building on the scientific basis already presented. The several aspects of technique are discussed, and an understanding of the relations between good technique and scientific awareness is shown to be fundamental to good vocal pedagogical practice. In differing ways all of the disciplines thus far discussed - history, the ethics and psychology, science, vocal technique - contribute to performance, which is the next topic dealt with. In addition, since the evaluation of performance is a question of aesthetics, that branch of philosophy is introduced as a further discipline contributing to the education of the fully equipped singer and vocal pedagogue. While a considerable amount of research has been undertaken by others on the individual disciplines discussed in this dissertation, no study to date has attempted the task of showing the inter-relationships of all of them, and the ways in which together they bear upon classical singing pedagogy. The central theme of the dissertation is that the adoption of a holistic, multidisciplinary approach is of particular benefit to singers and voice teachers, and that such an approach facilitates mutual co-operation between them and other voice professionals