This work focuses on developing and optimizing sound-absorbing underbody panels for vehicles, made from thermoplastic fibrous materials, to reduce tire-road noise; a concern becoming more prominent with the rise of electric vehicles. Previous studies showed that adding rigid embossed structures to the side opposite the noise source enhances effectively sound absorption, particularly in the critical frequency range for tire-road noise. This study extends this research by simulating the acoustic performance of this kind of underbody panels. Building on earlier findings, this paper presents a sensitivity analysis to identify the key geometrical and physical parameters influencing their absorption characteristics. Using Finite Element Method simulations, various configurations of height, material properties, and structural dimensions of the embossed structures were analyzed to determine their impact on sound absorption. The results indicate that specific parameters, such as height and material Air Flow Resistivity, significantly affect the absorption performance, particularly in the critical frequency range. This analysis provides valuable insights for optimizing the design of underbody panels to achieve maximum acoustic performance, contributing to the development of more effective noise mitigation solutions for modern vehicles. The findings underscore the importance of a detailed understanding of the physical and geometrical factors in designing efficient sound-absorbing structures.