In this thesis, we study the representation of speech signals and the estimation of information-theoretical measures from observations containing features of the speech signal. The main body of the thesis consists of four research papers. Paper A presents a compact representation of the speech signal that facilitates perfect reconstruction. The representation is constituted of models, model parameters, and signal coefficients. A difference compared to existing speech representations is that we seek a compact representation by adapting the models to maximally concentrate the energy of the signal coefficients according to a selected energy concentration criterion. The individual parts of the representation are closely related to speech signal properties such as spectral envelope, pitch, and voiced/unvoiced signal coefficients, bene cial for both speech coding and modi cation. From the information-theoretical measure of entropy, performance limits in coding and classi cation can be derived. Papers B and C discuss the estimation of di erential entropy. Paper B describes a method for estimation of the di erential entropies in the case when the set of vector observations (from the representation) lie on a lower-dimensional surface (manifold) in the embedding space. In contrast to the method presented in Paper B, Paper C introduces a method where the manifold structures are destroyed by constraining the resolution of the observation space. This facilitates the estimation of bounds on classi cation error rates even when the manifolds are of varying dimensionality within the embedding space. Finally, Paper D investigates the amount of shared information between spectral features of narrow-band (0.3-3.4 kHz) and high-band (3.4-8 kHz) speech. The results in Paper D indicate that the information shared between the high-band and the narrow-band is insufficient for high-quality wideband speech coding (0.3-8 kHz) without transmission of extra information describing the high-band. / QC 20100914

This thesis features a qualitative study of student source use and speech representation in two corpora of review essays that acknowledges the complexity of classroom writing contexts and the rhetorical nature of school genres. It asks how students engage with the texts they review, for what reasons, and in response to what aspects of the writing context. When considered as a distinct genre of student assignment, review essays make for a particularly interesting study of source engagement because they challenge students to maintain an authoritative voice as novices evaluating the work of an expert. In addition, citation issues in the review assignment might not be as obvious to students or their instructors as they would be, for instance, in a research paper for which multiple sources are consulted and synthesized. The review essays interrogated in this study were collected with appropriate ethics clearance from two undergraduate history courses. The analysis is extended to a small corpus of published reviews assigned as model texts in one of these courses. The study features a robust method that combined applied linguistics and discourse analysis to tease out connections between the grammatical structures of speech reports and their argumentative roles. This method involved a recursive process of classifying speech reports using Swales’ (1990) concepts of integral and non-integral citation, Thompson and Yiyun’s (1991) classifications of speech act verbs, and Vološinov (1929/1973) and Semino and Short’s (2004) models of speech reporting forms. In addition, the analysis considered the influence of the writing context on the students’ citation practices and took into account theories of rhetorical genre and student identity. The results show connections between assignment instructions and the effective and problematic ways students engaged with the texts they reviewed, such as a correlation between a directive to reduce redundancy and the absence of in-text attributions. Most notably, this study offers a fluid set of descriptors of the forms and functions of speech reports in student coursework that can be used by students, educators, plagiarism adjudicators, as well as scholars of rhetoric and composition, to illuminate some of the methods and motives of student source use.

This thesis features a qualitative study of student source use and speech representation in two corpora of review essays that acknowledges the complexity of classroom writing contexts and the rhetorical nature of school genres. It asks how students engage with the texts they review, for what reasons, and in response to what aspects of the writing context. When considered as a distinct genre of student assignment, review essays make for a particularly interesting study of source engagement because they challenge students to maintain an authoritative voice as novices evaluating the work of an expert. In addition, citation issues in the review assignment might not be as obvious to students or their instructors as they would be, for instance, in a research paper for which multiple sources are consulted and synthesized. The review essays interrogated in this study were collected with appropriate ethics clearance from two undergraduate history courses. The analysis is extended to a small corpus of published reviews assigned as model texts in one of these courses. The study features a robust method that combined applied linguistics and discourse analysis to tease out connections between the grammatical structures of speech reports and their argumentative roles. This method involved a recursive process of classifying speech reports using Swales’ (1990) concepts of integral and non-integral citation, Thompson and Yiyun’s (1991) classifications of speech act verbs, and Vološinov (1929/1973) and Semino and Short’s (2004) models of speech reporting forms. In addition, the analysis considered the influence of the writing context on the students’ citation practices and took into account theories of rhetorical genre and student identity. The results show connections between assignment instructions and the effective and problematic ways students engaged with the texts they reviewed, such as a correlation between a directive to reduce redundancy and the absence of in-text attributions. Most notably, this study offers a fluid set of descriptors of the forms and functions of speech reports in student coursework that can be used by students, educators, plagiarism adjudicators, as well as scholars of rhetoric and composition, to illuminate some of the methods and motives of student source use.