In this paper, we propose a method to optimize the sound absorption coefficient (SAC) of double-layer foam (DLF) absorbers via the equivalent-fluid approach and particle swarm optimization (PSO) technique. The acoustic performance of these DLF absorbers is predicted by theoretical models within a set of input parameters that include geometrical and transport parameters of the inner layers (i.e., foam layer). Using PSO technique, the optimal geometrical parameters of DLF structures for enhancing the SAC target in frequencies of interest. The observed results for low and middle frequency bands are given to illustrate the contribution of the proposed method.