## 2 Experimental Setup and Data Collection
### Laryngeal Flow Facility  
The synthetic VFs were mounted in a custom laryngeal flow facility driven by compressed air (\(\sim\)550 kPa) that was regulated down to 17.0 kPa via a Siemens 40-2 pressure regulator. The flow then passed through a Dwyer RMC 103-SSV flow meter that measured the volumetric flow rate and further regulated the flow before entering the vocal tract test facility shown in Figure 1b. The facility was comprised of a model lung plenum, which consisted of a 0.03 m\({}^{3}\) cylindrical chamber that was acoustically treated on the inside to reduce acoustic reflections. The plenum exhausted to a square tube, representing the trachea, with a cross-sectional area of 4.94 cm\({}^{2}\) and 48.0 cm in length. The subglottal pressure was measured with a flush-mounted Kulite ET-3 DC pressure transducer in the wall of the trachea tube, 3.8 cm upstream of the glottal exit.  
Two square mounting brackets that housed the synthetic VF models were attached at the exit plate of the tracheal tube. An inset within the tracheal tube transitioned the interior dimensions of the square tracheal tube down to 1.7 cm \(\times\) 1.7 cm over a length of 2.5 cm. While the medial-lateral dimension of each VF is 8.4 mm, an inset depth of 7.6 mm was machined into each opposing mounting bracket to hold the VFs. In this manner, the medial surface extended above the contacting surface of each bracket by 0.8 mm, such that when the opposing VFs were brought into contact the amount of medial compression could be adjusted.  
Two data sets were collected. The first positioned the VFs in a natural, uncompressed position such that there was no medial compression. The second incorporated a 0.8 mm shim between the opposing brackets when the medial surfaces were positioned in contact. This resulted in each VF being compressed by 0.4 mm in the medial-lateral direction. Anterior-posterior tensioning was applied in all cases by pulling on the string embedded in the models with a constant force of 0.3 N. Note that in this study there was no supraglottal tract, see Figure 1b.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**VF Layer** & **Material** & **Ratio (A-B-Thinner)** & **Young’s Modulus (kPa)** \\ \hline Body & Ecoflex & 1-1-1 & 11.8 \\ Ligament & Ecoflex & 1-1-4 & 2 \\ SLP & Ecoflex & 1-1-6 & 0.6 \\ Epithelium & Dragon Skin & 1-1-1 & 45 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Different mixture ratios of silicone and their corresponding Young’s moduli. A ratio of 1:1:x means that the layer was formed by mixing 1 part A, 1 part B, and x parts thinner by weight.  
Figure 1: (**a**) Model of the geometry of the silicone vocal folds; and (**b**) image of the experimental flow facility.  
High-speed video of the VF motion was acquired using an 8-bit IDT MotionPro X3 PLUS camera equipped with an Elicar V-HQ Macro 90 mm lens. In this study, an array size of \(484\times 504\) pixels was used with a frame rate of 2000 fps. The spatial resolution of the videos was \(24.4\,\mathrm{pixels/mm}\), corresponding to a physical area for each pixel of \(1.680\times 10^{-3}\,\mathrm{mm}^{2}\).  
For the case without medial compression, the VFs were driven with a subglottal pressure of \(1.00\,\mathrm{kPa}\). With medial compression, data were collected for subglottal pressures of \(0.91\), \(1.00\), \(1.09\), and \(1.18\,\mathrm{kPa}\), yielding average flow rates of \(236\), \(260\), \(291\), and \(307\,\mathrm{mL/s}\), respectively. HSV was recorded for \(1\,\mathrm{s}\) in each configuration, from which a \(300\,\mathrm{ms}\) segment was used to extract the GAW using segmentation [26].