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.