Sound focusing of a wavelength-scale gas-filled flat lens

The capability of focusing of a novel acoustic lens based on mesoscale acoustic cuboid particle filled with CO2 gas is analysed.This flat lens is able to focus sound in the same way that conventional curved acoustic lenses do.It is shown that the sound speed inside the cuboid is the responsible for this effect.By changing the percentage of CO2, the sound speed inside the cube changes and therefore the focusing properties.The focusing effect is numerically investigated and experimentally validated.The results obtained allow the design of new flat low cost acoustic lenses with wavelength-scale dimensions for different applications.