A soundproofing panel having a core sandwiched between a solid wall and a porous wall. The core being connected to the walls and having partitions extending in the thickness direction between the two walls so as to form cells. Each cell containing at least one sound energy dissipating layer constituted by hollow spherical beads having mutually contacting walls that are porous and micro-perforated, and being held in position in the thickness direction between the two walls by nets that are secured to the partitions.