## 4 Discussion
When the focus was positioned on the left side of the SCC (x \(<\) 0), clockwise endolymph flow was observed relative to the xy-plane, while shifting the focus to the right (x \(>\) 0) resulted in counterclockwise flow. Additionally, the displacement magnitude varied with focal position, with the largest displacement observed when the ultrasound was applied tangentially to the outer edge of the SCC. These results suggest that the direction and intensity of rotational sensations can be modulated by adjusting the focal position of the ultrasound. In conclusion, this study demonstrated the potential of LIFU to modulate rotational sensations through acoustic streaming in the SCC. With advancements in focused ultrasound technology, such as improved focal resolution, greater rotational sensations could be achieved with minimal temperature increase. Furthermore, this technique could evolve into a new form of direct vestibular stimulation by applying focus-variable ultrasound technology or multi-transducer array systems. To further validate the effectiveness of this stimulation method, experiments using a mock-up model of the SCCs will be conducted. These experiments will involve using a focused ultrasound transducer to induce fluid flow and monitor temperature changes within the model. The primary goal is to compare the results with simulation data and confirm the feasibility of the proposed stimulation method. The findings from these experiments will help validate the simulation results and provide direct evidence of the mechanical effects of ultrasound stimulation on the vestibular system. Additionally, this experimental validation will provide foundational data for more accurate predictions and applications of ultrasound-based vestibular stimulation in both clinical and experimental settings. There are still challenges in clinical applications due to several variables that must be considered. While previous studies have explored changes in the otoliths induced by LIFU [59] and the generation of endolymph flow near the cupula using acoustic frequency bands [29], the application of focused ultrasound has been more actively investigated in the fields of vascular and micromechanical research [54; 60]. To date, there has been a lack of research on the induction of cupula deflection via endolymph flow. Therefore, in this study, we compared our findings with those from research on cupula deflection induced by rotational movements [28; 52]. The research on cupula deflection induced by acoustic streaming from focused ultrasound is still in its early stages, and additional studies are needed. Additionally, the potential neuromodulatory effects of ultrasound on the vestibular system represent another avenue for exploration, as these effects could expand the application of LIFU beyond mechanical stimulation to include direct neural stimulation. This technology opens new possibilities for non-invasive vestibular stimulation by enabling control over both the intensity and direction of displacement through ultrasound parameters. With confirmed thermal safety, LIFU could be a promising method for future therapeutic applications. Further investigation into the long-term effects and clinical trials will be crucial for advancing vestibular disorder treatments and improving human balance control.