Developing a methodology to study the effect of the epilarynx tube on phonation threshold pressure and driving pressure

Linear source-filter theory of speech production has not yet sufficiently dealt with the lower vocal tract as an impedance matching region, and an energy feedback mechanism for self-sustained oscillation. An interactive nonlinear source-filter model is needed for this reason. Determining which model to use for studying lower vocal tract impedance effects becomes difficult, however. Human subjects do not offer sufficient access to the system. Physical models do not offer enough tissue-like biomechanical properties. Traditional excised larynx methodologies do not offer enough vocal tract involvement for any detailed nonlinear source-filter study. Computational simulation has already been used to identify the need for lower vocal tract interactive study, but needs experimental verification. As a result, methodological development seems to be a crucial next step.; The purpose of this research is to design a methodology that allows systematic variation of the epilarynx tube and glottal adduction, while collecting simultaneous intraglottal (driving) pressures during self-sustained oscillation. Since most of the historical data concerning excised larynxes made use of canine larynxes, it seemed logical to expand excised canine hemilarynx methodology to include the addition of a vocal tract with an epilarynx tube to study nonlinear source-filter interaction. Data collected on the effects of the epilarynx tube on intraglottal pressure yielded results generally consistent with the current body of research literature. However, phonation threshold pressure changes with epilarynx tube cross-sectional area did not agree with theoretical simulation, and may have been due to lack of sensitivity of the method, or perhaps due to the experimental design protocol. The data did reveal trends in phonation threshold pressure consistent with principles of impedance matching. The methodological design does seem to have certain promise for extending the current understanding with respect to impedance matching and nonlinear source-filter theory.