Influence of Oropharyngeal Esophageal Cavity Geometry and Beak Angle on Vocal Tract Resonance of Birds using Computational Modeling

Birds produce complex vocalizations through coordinated motor systems, with the syrinx producing sound and the trachea, beak, and other structures modifying it. The bird’s vocal tract includes resonating cavities such as the oropharyngeal esophageal cavity (OEC), which shapes the sound produced by the syrinx. We developed computational models of a bird’s upper vocal tract based on micro-CT scans, including three models. The first is the Primary Model, while the others are Refined Models with two different OEC geometries: a cylinder (RM<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</inf>) and a truncated cone (RM<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf>). Using COMSOL Multiphysics, we analyzed both the impact of the OEC on resonance and the influence of different OEC shapes on sound production. Validation with bird’s vocalizations showed that the truncated conical OEC most accurately matched the observed resonant frequencies.