Design and measurements of a broadband two-dimensional acoustic lens

We describe the design, fabrication, and measurement of a 2D broadband gradient index acoustic lens in air. The index of refraction is tuned by controlling the dimensions of acoustic metamaterial unit cell inclusions designed through numerical simulations. The lens was fabricated in plastic through rapid prototyping stereolithography, and measurements of the sound field show good agreement with the theoretical lens performance. The broadband performance of the lens is confirmed for frequencies ranging from 1.5 kHz to 4.5 kHz.