<p>Enhancement of the amplification factor with minimal stress is one of the persistent challenges in ultrasonic horn design. The present study aims to investigate the effect of hollow horn geometries viz. triangular, square, hexagonal, octagonal, and circular configurations on modal and harmonic characteristics. At first, modal analysis is performed to determine the natural frequency and mode shapes for each horn topology. Thereafter, the design feasibility is performed through harmonic analysis to find the amplification and stress developed in horn geometry. Additionally, the implication of hollow horn height and diameter of best-performing horn topology is studied for modal and harmonic analysis. The finite element method is employed to solve governing equations and boundary conditions. Our study reveals that the highest Eigen frequency is observed for hollow circular horn configurations. Moreover, this geometry also generates the highest displacement amplitude and von mises stress within the endurance limit and therefore is proposed for optimum geometry design. Furthermore, the displacement amplitude is seen as highest for hollow horn configuration when the hollow horn height is half of its entire length. However, the triangular hollow horn configurations have the lowest displacement amplitude and act as the worst case. Additionally, the increment in diameter of the hollow horn leads to an increase in displacement amplitude and von mises stress. The present investigation gives insights into different hollow horn topology and their performance in modal and harmonic analysis, which can be utilized in industries like aerospace, automobile, etc.</p> Graphical Abstract <p></p>