Refractive acoustic devices for airborne sound

It is shown that a system made of periodic distributions of rigid cylinders in air acts as a new material which allows the construction of refractive acoustic devices for airborne sound. This kind of crystal, named sonic crystal, has low impedance and transmits the sound at subsonic velocities. Here, the fabrication and characterization of a convergent lens is presented. Also, the acoustic analog of the Fabry–Perot interferometer based on this crystal is analyzed. It has been concluded that refractive devices based on sonic crystals behave in a manner similar to that of optical systems. [Work supported by CICyT of Spain.]