The application of ultrasonic cavitation in chemical processing is a widespread method to accelerate dissolution processes. In recycling technology, often bulk material is introduced into a reactor forming a packed bed of granular particles. Thereby, the cavitation activity at the material surfaces is of interest. In this numerical study, the packed bed is simplified by sphere packings of different arrangement and porosity. The ultrasound propagation model considers the effect of cavitation bubbles by a linearized damping ansatz. A strong sound scattering by the spheres is found for packings with low porosities, while the sphere arrangement is less important.