## 3 Sensitivity of the Intraglottal and Vocal Fold Contact Pressures to Sensor Position
### Methods
#### 3.1.2 Laryngeal Flow Facility  
The flow facility, shown in detail in Figure 9a, utilized compressed air at 700 kPa that was regulated to 17 kPa by a Siemens 40 - 2 pressure regulator. The flow entered a Dwyer RMC 103-SSV flow meter that measured the mean flow rate, and further regulated the pressure. The flow then entered a 0.3 m\({}^{3}\) cylindrical plenum, representative of the lung volume. The inner walls of the plenum were insulated acoustically by foam. A 15 cm long, 2.13 cm\({}^{2}\) cross-sectional area rectangular channel, representing the trachea, exited the chamber. The length of the channel was selected based on the results of numerical simulations of one-dimensional wave propagation that match the resonances of the subglottal pulmonary tract. Two opposing brackets that act as flanges were bolted to the end of the tracheal channel. Each bracket had a rectangular cut out in the middle; a synthetic VF model (see Section 3.1.1) was mounted in one, while the other allowed access for a moveable contact plate, against which the VF vibrated. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Layer**} & **Physiological Range** & **Vocal Fold Model [Std. Dev.]** & **Silicone Ratio** \\  & **(kPa)** & **(kPa)** & **(Type of Silicone)** \\ \hline Adipose & \multirow{2}{*}{1 – 10 [39]} & \multirow{2}{*}{6.8[0.0058]} & \multirow{2}{*}{1 : 1 : 4 (EF)} \\ tissue & & & \\ Body & 1.5 – 50 [35; 41; 42] & 17.3[0.042] & 1 : 1 : 2 (EF) \\ Cover & 1 – 8 [35; 36] & 0.95[0.053] & 1 : 1 : 8 (EF) \\ Epithelium & Not available & 101[1.4] & 1 : 1 : 1 (DS) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Vocal fold model and physiological values of the moduli of elasticity for the different layers of the vocal folds. Smooth-On® Ecoflex 0030 and Dragonskin Silicone mixtures are denoted by (EF) and (DS), respectively. Figure 9: **(a)** Schematic of the experimental flow facility. **(b)** A close-up view of a section, and a top view, of the moveable contact plate with the embedded pressure transducer and copper contact strip. All dimensions are in mm. The VF model mounted in the bracket is shown in Figure 10. The depth of the VF cut-out was 6.5 mm, which resulted in the medial edge of the VF model protruding \(\sim\)1.25 mm above the top edge of the bracket. Shims were placed between the two opposing brackets to control the medial prephonatory compression (MPC) of the VF, which could be adjusted over a range of 0-1.25 mm, and corresponded to the distance the model was deformed into the wall. The resultant static pressure at the corresponding MPC is referred to as the medial prephonatory pressure (MPP). At the inferior end of the bracket (not visible in Figure 10), the cut-out depth stepped up by 1.5 mm. This ensured that the AT layer was embedded in the lateral wall, and that the inferior, angled surface of the VF model rose up from the lateral wall, as is shown schematically in Figure 9a. A 17.0 mm wide moveable contact plate was manufactured from polyactic acid (PLA) via rapid prototyping, and was placed in the channel of the opposing bracket (see Figures 9b and 10). It was centered under the VF model, creating a flat surface against which the VF vibrated. The plate extended the length of the tracheal channel. Superiorly, it extended past the exit plane of the VF model by \(\sim\)10.0 cm, where it was attached to a Thorlabs PT1 (Thorlabs, Newton, NJ, USA) linear slide that included a micropositioner with a Vernier scale. This allowed the inferior-superior position of the slide to be controlled with an accuracy of 0.025 mm. The unsteady subglottal pressure was measured with a Kulite ET-3 DC (Kulite Semiconductor Products, Inc., Leonia, NJ) pressure transducer with a 6.35 mm diameter sensing diaphragm that was flush-mounted in the wall of the tracheal channel, and positioned 3.0 cm upstream of the VF entrance plane, as shown in Figure 9a. The subglottal pressure transducer has a FSO of 13.8 kPa with an accuracy of 0.5% FSO and a flat frequency response from DC to 2.5 kHz.