Acoustic Duct Filter Optimization via Rigorous Analysis

This paper presents a computationally efficient approach for the design of acoustic duct filters composed of axisymmetric step discontinuities. A rigorous approach based on the mode-matching technique and the building block method is employed to model sound propagation and compute transmission loss across a cascade of circular duct segments. Unlike existing studies relying on empirical approximations or simulations, the proposed method retains wave-theoretical accuracy while enabling fast evaluations suitable for iterative optimization. In optimization, some global metaheuristic algorithms are coupled with a local search phase to ensure both broad design space exploration and fine-tuned convergence near local optima. The methodology is validated through the design of some filters for frequency bands of practical importance.