The mechanical response of ductile and porous materials under dynamic loading is of interest for a wide range of applications, particularly in the nuclear, defense and aerospace sectors. Under high strain rate loading, the local accelerations near the cavities wall play a fundamental role on the macroscopic behavior of the porous material [1]. It has been shown that the size and shape of the pores have a strong effect on the dynamic behavior of the porous material. Furthermore, the effects of size distribution and/or void volume fraction have been demonstrated for spherical cavities in materials subject to dynamic loading conditions encountered in planar impact experiments [2]. We analyze here a numerical representative volume element (RVE), consisting of a cubic unit cell containing two families of pores embedded in an elastic-perfectly plastic matrix. The RVE is subject to spherical loading under homogeneous kinematic boundary. Multiple microstructures are considered by varying the number of voids, their position, and their size intending to evaluate the micro-inertia contribution to the overall macroscopic stress. First, when the two populations are identical, our results allow to identify the adjustment needed in theoretical approaches (developed for spherical voids surrounded by a spherical matric) to perfectly match finite element results for various initial void sizes. A sound analysis of the velocity field within numerical RVEs is next proposed to reveal the void interaction, for several configurations, taking place under dynamic loading.