## 1 Introduction  
Today, developing new medical methods for preventing and treating voice disorders have high relevance. Those could improve the ability of early diagnosis e.g., in the case of cancer occur and eventually could help faster treatment and rehabilitation of patients. The vocal folds are the main organ in human voice production, the vocal folds' sound emission is the major interest of many investigations in this area [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15]. The determination of mechanical properties of synthetic as well as natural vocal fold material is an important task for further understanding of the phonation process. Consequently,numerous studies [16; 17; 18; 19; 20; 21] have been focused on the analysis and development of synthetic vocal folds. In particular, silicone or polyurethane mixtures are used to produce vocal fold models [22; 23; 24; 20], which is the target of the research of this study. This work presents a method to measure the elastic modulus of four silicone rubber samples with different stiffness ratios as a function of frequency similar to the vocal fold tissue that exhibits frequency-dependent parameters [25]. Our focus is on the pipette aspiration method that was originally introduced by [PERSON] and [PERSON] [26] to measure the stiffness and intracellular pressure of red blood cell membranes. Therein, a pipette was placed on the sample and, via a static low pressure, the sample surface was sucked into the pipette. A related method using a suction cup tool was used to measure the skins' biaxial membrane properties [27]. The pipette aspiration method was later improved for a cultured cell treating application [28; 29]. This method was improved upon more by [PERSON] [30]. The pipette aspiration method application for estimating the elastic modulus of soft tissues was presented in [31; 32]. [PERSON] et al. [33] applied it to a local elasticity measurement of soft tissue and a simple equation developed to calculate the static elastic modulus of the tissue. In his measurement setup, the soft tissue floated in a salt bath to counteract the compression force of the pipette tip on the sample surface. The equation was developed for a static measurement setup while the vocal folds' modulus of elasticity is a function of frequency. Therefore, a lack of dependency of the equation terms on the excitation frequency and absence of the pipette wall force and friction influence on the vibrational behavior of the sample surface can be seen in the equation. Although, frequency-dependent analyses in a range of 0 Hz to 50 Hz have been done by previous studies [34; 35; 36; 37] to investigate the local elastic modulus of real and synthetic vocal fold tissue. However, the examined range is not wide enough to cover the human speech sound frequency [38]. A frequency-dependent analysis in the frequency range of human phonation using the pipette aspiration method was first presented by [PERSON] et al. [39]. In the suggested setup, the silicone sample was placed under the pipette and it was lowered onto the sample taking special care that the pipette does not act any force onto the silicone, which would affect the results. By means of a pistonphone that was mounted on an electromechanical shaker, a fluctuating pressure was generated within the pipette. The out-of-plane velocity at the centre of the specimen's surface within the pipette was measured by a laser scanning vibrometer. [PERSON] et al. [40; 41; 42] enhanced the setup of [PERSON] et al. [39] to suggest a reliable pipette aspiration method for spatially-resolved material characterization of synthetic vocal folds over a frequency range of 50 Hz to 700 Hz. Unlike the [PERSON] et al. [33] method to counteract the pipette wall force on the sample surface, [PERSON] et al. [40] limited the force to 0.1 N for all the mixtures in the frequency range. However, those measurement setups are not accurate enough to measure frequency-dependent material properties of anisotropic and inhomogeneous materials as existent in vocal folds.