Squeezed waveguides as a framework to study vowel-like acoustic resonances

The relationship between vocal tract geometry and acoustic resonances is often examined using speaker-specific data, limiting physical studies to a narrow set of static, rigid configurations and frequently producing discontinuous area functions that are poorly suited for studying dynamic vocal-tract behavior. To address these constraints, this study introduces a theoretical squeezed waveguide vocal tract (SWVT) framework for analyzing the relationship between acoustic resonances (up to 4-5 kHz) and smooth area functions that characterize vowel-like vocal tract configurations with one or two constrictions. The relevance of seven SWVT parameters-constriction positions, degrees, extents, and waveguide length-is established through theoretical analysis and experimental validation. Experiments are performed using both rigid, static waveguides and a deformable, molded waveguide. The molded waveguide facilitates experimental investigation of constriction degrees up to full closure and provides a basis for future studies on the (aero-)acoustic-geometry relationship in dynamic SWVT configurations.