A subwavelength insulation panel for acoustic and aeroacoustic sources

A new kind of panel with strong transmission loss, breaking the mass law by 15 dB and composed by a soft solid plate with embedded solid cylindrical inclusions is studied numerically and experimentally. The presence of the inclusions introduces resonant and antiresonant phenomena in the subwavelength regime (the thickness is 30 times smaller than the equivalent wavelength in air), leading to an elastic band-gap and a destructive modal interference able to interact with each other. We also report on an experimental campaign demonstrating that the panel is very effective at insulating aeroacoustic sources (tested up to Mach 0.6), showing even better performance than with an acoustic source excitation. A new analysis tool, the vibroacoustic band diagram, is introduced to better apprehend theoretically all these results.