Wood anomalies in lattices of cylindrical perforated shells

The enhancement of sound absorption by the excitation of Wood anomalies in slabs of cylindrical perforated shells is here studied. These scattering units have low losses when the diameter of the perforations is on the order of hundreds of microns or higher. It has been observed that slabs consisting of a few layers of perforated shells exhibit high levels of absorption that cannot be explained in terms of the dissipative properties of a single scatterer. This behavior is explained by the excitation of resonant Wood anomalies that redirect the sound perpendicularly to the incident direction. Thus, energy dissipation is obtained from the long path that the sound wave travels inside the slab.