A numerical simulation of the flow-excited acoustic resonance for the case of two side-by-side cylinders in cross-flow is performed. One spacing ratio between the cylinders, T/D = 2.5, is investigated, where D is the diameter of the cylinders and T is the center-tocenter distance between them. The unsteady flow field is simulated using a finite-volume method at a Reynolds number of 30000. This simulation is then coupled with a finite element simulation of the resonant sound field, by means of Howe's theory of aerodynamics sound, to reveal the details of flow-sound interaction mechanisms, including the nature and the locations of the aeroacoustic sources in the flow field. At the off resonance conditions the vortex shedding from the cylinders occurs at a single frequency with a Strouhal number of 0.217. Moreover, a symmetric wake structure downstream of the two cylinders is observed. However, when acoustic resonance is initiated the symmetric wake structure downstream of the cylinders is eliminated and the vortex shedding from both cylinders becomes antisymmetric. Moreover, two main aeroacoustic sources located just downstream of each cylinder are observed. The numerical results are compared with the experimental results presented in a previous investigation and favourable agreement is obtained.