Vocal tract (half-width ∝ √area)
Glottis (source end, left)
Human vowels get their distinct timbre from resonances of the vocal tract, not from the vocal folds themselves. This 2D counterpart models the tract as the same chain of cylindrical tube segments as the 3D lab — a real multi-tube acoustic transmission-line model — but lets you shape it by dragging a constriction point directly across a top-down cross-section: sideways moves the constriction from pharynx to lips, and toward/away from the centerline sets how tight it is, alongside sliders for lip rounding and tract length. A frequency sweep solves the complex input impedance of the chained tube at the glottis, and its resonance peaks are read off directly as the formants F1, F2 and F3 that define vowel identity. Five cardinal-vowel presets snap the tract to textbook articulations, and a live F1/F2 chart shows where your shape lands inside the classic IPA vowel quadrilateral.