# Acoustic and Aerodynamic Coupling during
## 3 Results and Discussion  
### Oscillation Frequency and Mean Subglottal Pressure  
The mean subglottal pressure \(p_{sub}\), the volume flow rate \(\dot{V}\), and the fundamental oscillation frequency \(f_{0}\) for the different VT replicas are listed in Table 1. The values were acquired for stable vocal fold oscillation at a subglottal pressure slightly above the physiological oscillation threshold. According to Table 1, the three parameters vary for the different VT replicas. The fundamental frequency is increased for the configurations with VT replicas in comparison to the configuration without VT. The shift of the fundamental frequency is less than 10% for all VT replicas, with the exception of the simplified replicas of subject 1 and subject 2. The simplified replica of subject 1 exhibits a decreased fundamental frequency by 7% and the fundamental frequency of the simplified subject 2 replica is increased by 51%. Between the realistic and simplified VT replicas no systematic variation of the fundamental frequency could be identified. [PERSON] et al. [27] reported that acoustic coupling between the vocal folds and the VT leads to frequency jumps when the oscillation frequency crosses a resonance frequency of the VT. However, they induced this effect with a variation of the VT length between 1.6 and 245.6 cm. As the length of the VT replicas used in this study differs by less than 5%, we assume that the variation of the fundamental frequency cannot be explained by this parameter. The deviation of the fundamental frequency for the simplified replica of subject 2 may be due to a change of the oscillation mode of the vocal folds. The back-coupling due to the specific VT geometry seems to be beneficial for that different modal behavior. However, the present measurement data is insufficient to prove that assumption. The volume flow rate and the subglottal pressure are reduced by the VT in comparison to the configuration without VT for all replicas with the exception of the realistic and simplified replica of subject 2, which exhibit an increase of 2% and 20%, respectively, for the subglottal pressure \(p_{sub}\) when related to the configuration without VT. The comparison of the subglottal pressure and the volume flow rate between the realistic and simplified replica shows no consistent behavior. For subject 1, subject 5 and subject 6, the volume flow rate and the subglottal pressure are reduced up to 73% and up to 37%, respectively, for the simplified replica. For the simplified replica of subject 2, both volume flow and subglottal pressure are increased by 18% and 91%, when respectively, compared to the realistic replica. For subject 3 and subject 4, the influence of the simplification on subglottal pressure and volume flow rate is different. Whereas for subject 3 the volume flow rate is decreased by 9% and the \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Configurations** & \(p_{sub}\)**/Pa** & \(\dot{V}\)**/L/min** & \(f_{0}\)**/Hz** \\ \hline without VT & 4691 & 147 & 149 \\ \hline subject 1—realistic & 4179 & 56 & 149 \\ subject 2—realistic & 4781 & 68 & 155 \\ subject 3—realistic & 3960 & 115 & 156 \\ subject 4—realistic & 4047 & 65 & 159 \\ subject 5—realistic & 4481 & 68 & 156 \\ subject 6—realistic & 3923 & 60 & 157 \\ \hline subject 1—simplified & 2769 & 15 & 139 \\ subject 2—simplified & 5638 & 130 & 225 \\ subject 3—simplified & 4043 & 105 & 160 \\ subject 4—simplified & 3313 & 86 & 162 \\ subject 5—simplified & 2823 & 41 & 154 \\ subject 6—simplified & 2493 & 25 & 151 \\ \hline mean VT & 3881 & 78 & 164 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Physical parameters of the mean subglottal pressure \(p_{sub}\), the volume flow rate \(\dot{V}\), and the fundamental oscillation frequency \(f_{0}\) as measured in our experimental setup. subglottal pressure is slightly increased by 2%, for subject 4 the subglottal pressure is decreased by 18% and the volume flow rate is increased by 32%.