## 3 Sensitivity of the Intraglottal and Vocal Fold Contact Pressures to Sensor Position
### Results
#### 3.2.3 Sensitivity of Intraglottal and Vocal Fold Contact Pressures to Sensor Position  
Figure 15 presents 7 intraglottal pressure waveforms as a function of the inferior-superior position of the intraglottal pressure transducer, relative to the midpoint of the contact location, for the same measurements reported in Section 3.2.1 (\(p_{s}=2.15\) kPa, \(Q=409\) mL/s, \(f_{o}=168\) Hz, \(E_{c}=0.95\) kPa, MPC = 0.75 mm, and MPP = 1.45 kPa). Using the Wheatsoe bridge arrangement, the inferior-superior contact length was measured to be 2.95 mm. The coordinate system is defined such that \(x=0\) corresponds to the midpoint of VF contact with increasing positive values indicating the superior direction (denoted by solid lines of decreasing grayscale value), and negative values indicating the inferior direction (denoted by dashed lines of decreasing grayscale value). The contact pressure measurement locations that are plotted include \(x=0\) mm, \(\pm 0.5\) mm, \(\pm 1.0\) mm, and \(\pm 2.0\) mm, measured from the inferior-superior midpoint of VF contact to the inferior-superior midpoint of the contact sensor. Remember that the sensing window placed in the moveable contact plate is 1.3 mm long in the inferior-superior direction. Based on the length of contact in the inferior-superior direction, a portion or all of the pressure sensor will move outside the region of VF contact for locations at which \(x\geq 0.825\) mm. That is, the sensor location of \(x=0\) mm corresponds to the midpoint of contact, with the sensing window completely covered during contact. For the locations of \(x=\pm 0.5\) mm the sensing window is still completely covered during contact. When the sensor is positioned at \(x=\pm 1.0\) mm, the sensor is only partially covered during vocal fold contact, with part of it exposed to either the supraglottal, or subglottal pressure, respectively. Finally, for a position of \(x=\pm 2.0\) mm the sensor does not experience any contact, and is only measuring the supraglottal and subglottal pressure, respectively. The maximum value of the contact pressure occurs when the intraglottal pressure transducer is centered about the midpoint of contact. Small adjustments in the position of the transducer (\(\pm 0.5\) mm) lead to deviations in the peak contact pressure of up to 20%. Remember, these positions still correspond to the sensor being contained within the contact region. As the pressure sensor is moved inferiorly from the midpoint of VF contact, the primary and secondary peaks merge, and the waveform begins to resemble the subglottal pressure signal. In particular, the minimum pressure value immediately following contact rises. This behavior can also be observed by comparing the waveforms at the midpoint of contact between Figure 15 and Figure 14, where only the subglottal pressure has changed. Note, the amount the pressure drops between the two peaks varies for these two scenarios. This arises due to very slight changes in the VF kinematics. Note that in Figure 14 the contact peak occurs at \(t\simeq 3.6\) ms. The secondary peak is reached when the inferior edge of the VF fold begins to open, exposing the sensor to the subglottal pressure, which occurs at  
Figure 14: Intraglottal pressure waveform for \(p_{\mathrm{sub}}=2\) kPa averaged over 100 cycles. \(t\simeq 5.5\,\)ms. In Figure 15 peak contact occurs at \(t\simeq 3.6\,\)ms, but the secondary peak occurs at \(t\simeq 4.6\,\)ms; that is, the sensor is exposed to the subglottal pressure \(\sim 0.9\,\)ms sooner. This results in the pressure signal not decreasing as much, and rising back to the secondary subglottal pressure peak sooner. This same phenomenon is observed in Figure 15, where as the sensor moves inferiorly from the midpoint of contact, the minimum pressure that is reached in the valley between the contact and subglottal pressure peaks increases as the sensor is exposed to the subglottal pressure sooner, as seen in the case of \(x=-0.5\,\)mm.