Passive directivity detection of acoustic sources based on acoustic Luneburg lens.

This article reports an acoustic Luneburg lens (ALL) design with graded refractive index for passive directivity detection of acoustic sources. The refractive index profile of the lens is realized based on square pillars with graded variation of their dimensions. Numerical and experimental studies are conducted to investigate the performance of directivity detection. The results demonstrate that the lens designed and developed in this study is capable of precisely detecting the directivity of one acoustic source. Furthermore, the directivities of two acoustic sources can also be detected with a resolution of 15°. In addition, different methods are investigated, including introducing phase difference by tuning input signals or moving ALL, and increasing the aperture size of ALL, to improve the resolution of dual sources directivity detection.