Soundproof panel

Soundproof panel (10) that is transmission-efficient and has a sandwich structure, comprising:

• two outer walls (1, 2) parallel to one another;
• a core (3) rigidly connected to the outer walls so that shear stresses are transmitted between said core and each of the outer walls, and the core maintaining the outer walls apart from each other so as to delimit an intermediate space;
• and
• modifying elements (4) contained in the intermediate space, and maintained by the core at locations which are fixed with respect to directions parallel to the outer walls;
• wherein an acoustic wave (IW) which is incident onto one on the outer walls (1) is transformed into a stationary bending vibration of the panel (10), said stationary vibration being a superposition of normal modes of the panel that are excited by the incident acoustic wave, and a transmitted acoustic wave (TW) which emerges from the other outer wall (2) results from emission contributions generated by the excited normal modes,
• wherein the locations of the modifying elements (4) in projection onto a surface parallel to the outer walls (1, 2) form a fractal distribution with a base pattern which is implemented by autosimilarity at least once, said fractal distribution being such that normal modes of bending vibration of the panel, called concentrated modes, have vibration antinodes with non-zero amplitude only inside a restricted zone of the panel which is surrounded by at least some of the modifying elements contributing to the fractal distribution,
• so that the transmitted acoustic wave (TW) results only from emission contributions which are generated inside said restricted zone of the panel when the excited normal modes are all concentrated modes.