Fig 1. Schematic (not to scale) of the experimental setup testing a physical model (blue region) in a syrinx or larynx position.

The microphone was placed 10 cm downstream from the opening of the vocal tract. Pressure transducers (P1, P2) were placed below the respective sound sources. A 15l expansion chamber simulated acoustic properties of the lung. Flow rate was measured upstream from the expansion chamber. Trachea length was varied between 0 cm and 248 cm.