## 7 Conclusions  
We presented a measurement method to determine the frequency-dependent elastic modulus of silicone rubber mixtures that are used for synthetic vocal folds models. Therewith, a silicone specimen was placed under a pipette, which is used to channel the acoustic pressure generated by a tiny loudspeaker. Two different conditions were defined for pipette sample cross-section boundaries. First, the pipette was pressed against the sample surface by applying several contact forces in the range of 0 to 100 mN. Second, the pipette was placed on the surface with a very small gap. The calculated elastic modulus for the four silicone mixtures shows an increase over the frequency range and was in the range of 2.1 kPa to 90 kPa for the smaller pipette. To verify the functionality of the presented measurement setup for characterization of the dynamic material properties of the silicone rubber and real tissue, numerical simulation by a finite element method using a simplified model of the experimental setup was performed under the two boundary conditions that exhibit a significant difference in the results. The influence of the harmonic excitation on the model [PERSON]'s modulus, Poisson's ratio, the damping factor and resonance behavior of the surface was discovered by the simulation. [PERSON]'s modulus and damping factor of the model increase over the excitation frequency range. The results show that the damping factor of the model is frequency-dependent and 0.13 for 50 Hz and 0.25 for 500 Hz and cannot be assumed constant over the human speech frequency range, while the Poisson's ratio was close to 0.5 and can be assumed constant in the frequency range, as shown in the previous studies [39; 40; 54; 55]. Since the lack of the equation dependency on the excitation frequency, resonance effect and the absence of considering the impact of the pipette tip wall force and friction was revealed in the measurement and simulation results, it can be concluded that the [PERSON] et al. [33] analytic approximation cannot be used for a dynamic measurement in the range of human speech frequency [38]. We modified the [PERSON] et al. Equation (1) by adding a frequency-dependent factor to calculate silicone rubber elastic modulus at the two boundary conditions. Recalculating the samples modulus of elasticity with the new analytical approximations made the results of measurement fit well with model Young's modulus in both boundary conditions. Consequently, the presented acoustic pipette aspiration method has the precise capability to calculate the material frequency-dependent properties (e.g., modulus of elasticity). Using a gap can cancel the impact of the pipette tip compression force and friction, which are the major causes of uncertainty, but, if a connection between the pipette and the surface is unpreventable, the contact compression force should be restricted to absolutely zero. Moreover, since the frequency-dependent relationship between the displacement profile and the pipette radius was seen because of the surface resonance, the radius could not exceed a certain limit in a dynamic measurement. Furthermore, the measurement results revealed (see e.g., Section 5.1.1) that the displacement profile has a linear relation with the excitation pressure at a fixed frequency when the pipette is connected to surface by a fixed compression force and the pipette radius diversity cannot affect this linear relationship in this present method. The present results were in good agreement with the corresponding analytical results obtained by [PERSON] et al. [40] and [PERSON] et al. [39]. Extreme miniaturization and simplicity of the presented measurement setup are the key benefits of the developed method in comparison to the previous studies using a pistonphone. Further work is underway toward investigations on excised tissue and the comparison of real and synthetic vocal folds material characterization. Since the displacement was measured by a laser vibrometer, the poor reflectivity and roughness of real tissue might be a challenging issue.