## 1 Introduction
The hair cells of the basilar membrane are specialized sensory receptors located within the cochlea of the inner ear. These cells play a critical role in the process of hearing by converting mechanical vibrations into electrical signals that can be interpreted by the brain. They are situated along the length of the basilar membrane, which is tonotopically organized, meaning different regions respond to different sound frequencies. Therefore, the sound transmission from the outer ear to the inner ear can be considered as a form of energy transfer induced by the sound pressure on the eardrum towards the cochlea, where sound is converted into electricity. Thus, while hearing, energy is not only transferred, but transformed into a different form as well. It is thought that the amplitude of stapes vibration and the volume of fluid oscillating near the OW are key indicators of the cochlea's input impedance [2; 3; 4]. Empirical studies have demonstrated that for frequencies below 2000 Hz, the volume of vibrating fluid adjacent to the OW is comparable in magnitude to that near the RW, with vibrations occurring in opposite phases [5; 6]. Thus, to evaluate cochlear stimulation in the low frequency range (up to 2000 Hz), either the volume of the vibrating fluid near the RW or the amplitude of the RW membrane's vibrations can be used as estimators. This becomes particularly important in situations where predicting cochlear stimulation is difficult, such as after the implantation of various prostheses that transmit vibrational energy to the cochlea instead of the immobilized stages footplate (in stapedotomy or stapedectomy procedures). In these specific situations, the resulting effects can be assessed by measuring the vibrations of the RWM under physiological conditions [7]. To gain a deeper understanding of the role of the RWM in healthy, diseased, and implanted ears, several finite element (FE) models of the human ear have been developed. These models typically include the middle-ear cavity, RWM, cochlea, ossicles, and tympanic membrane. Numerical studies proposing different FE models have been reported by [PERSON] and [PERSON] [8], [PERSON] et al. [9], and [PERSON] and [PERSON] [10]. However, in these analyses, the mechanical properties of the RWM were only estimated based on some theoretical assumptions due to lack of reliable data in the literature [11]. The phenomena occurring within the inner ear, particularly the transmission of vibrations from the auditory ossicles to the fluid in the cochlea, can be also analysed using other numerical methods. Reliable results can be achieved by Fluid-Structure Interaction (FSI) methods. Within this framework, two general main approaches can be used to solve the posed problem. The first is the monolithic approach, which employs specialized software that integrates both fluid and solid domains into a single system, solving them simultaneously. The second, simpler but more commonly used, is the staggered approach, where separate solvers handle the fluid and solid domains. Typically, a computational fluid dynamics solver is used for the fluid domain and an FE engine is used for the structural domain, both exchanging information during each time step, ensuring the full consistency of the results achieved through this coupling [12]. In the staggered approach, two levels of coupling can be distinguished: weak and strong. In the weak one, solvers exchange information once per time step, while in the strong coupling scenario, additional iterations within each time step are run to ensure improved accuracy and numerical stability. Although strong coupling is advantageous, particularly for nearly incompressible fluids [12], it is computationally much more expensive.