A study of voice production in normal and dysphonic subjects

Kelman, Andrew W (1977) A study of voice production in normal and dysphonic subjects. PhD thesis, University of Glasgow.

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Abstract

The aims of the research described in this thesis were to investigate some of the factors involved in voice production, and to develop some of the techniques employed, to a stage at which they could be used clinically to assess phonatory function. Available techniques for assessing vocal performance were completely subjective, and, thus, there was a great need to provide objective means of measuring the degrees of vocal dysfunction of the many patients attending the Speech Therapy Department. In: CHAPTER 1, the vocal tract and musculature of the larynx and vocal folds are described. The Myoelastic-Aerodynamic theory of vocal fold vibration is briefly discussed, and a review of some of the relevant literature is given. The instrumentation used in the study is detailed in CHAPTER 2. The maintenance and control of air flow is of prime importance to voice production, and in CHAPTER 3, aerodynamic measurements are utilized in providing two series of tests which can be used to assess phonatory function-. These are now used routinely in the Speech Therapy Department. The production of voiced sounds depends upon the interruption of the air supply from the lungs by the regular vibration of the vocal folds. Thus the frequency spectra of voiced sounds, and in particular of vowel sounds, consist of harmonic series, with regular frequency components. The frequency analysis of vowel sounds is described in CHAPTER 4, and the presence of abnormal components related to dysphonic conditions. The results obtained from an assessment based on spectral analysis (due to Yanagihara) are compared to those obtained from the aerodynamic assessment developed in CHAPTER 3, with the latter assessment proving of greater value as a routine clinical technique. The vibratory pattern of the vocal folds is studied in CHAPTER 5 using the non-invasive laryngo-graph technique. The period of major excitation of the vocal tract, i.e. the closing phase of the vocal fold vibration, is related to certain properties of the spectrum of the laryngograph waveform, namely the spectral gradient and also the presence of fine structure in the spectrum. Abnormal spectral components in the voice spectra are shown to originate from the vocal fold vibratory pattern, and a simple model of the vocal folds is used to explain some of the phenomena. In CHAPTER 6 the control of a sustained vowel phonation is discussed, and the relationships between air flow rate, sound level and the vibratory pattern of the vocal folds are studied. In CHAPTER 7 the electromyographic activity associated with the lip musculature, during the production of a consonant - vowel - consonant syllable, is- studied. The differences in the outputs obtained using different electrode sites and configurations are explained, and the measured activity attributed to different muscle groups by a process of spatial mapping. The main results of the experiments are summarized in CHAPTER 8. This research has led to a greater understanding of the processes involved in voice production, and also to the development of objective techniques which can be used directly in the assessment of dysphonic patients.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Andrew Watt Kay
Keywords: Speech therapy
Date of Award: 1977
Depositing User: Enlighten Team
Unique ID: glathesis:1977-72276
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 May 2019 15:12
Last Modified: 24 May 2019 15:12
URI: http://theses.gla.ac.uk/id/eprint/72276

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