Improving the Directionality of Low-Frequency Acoustic Radiation by a Finite Array of Quadrupolar Sources with Acoustic Metamaterials

Manipulating radiation patterns is challenging, especially at low frequencies. In this paper, we demonstrate that acoustic metamaterials arranged as an array of quadrupoles remarkably improve the directionality of acoustic radiation at low frequencies, compared with previous metamaterials arranged as monopole and dipole structures. The directivity of the acoustic radiation can be adjusted by changing the characteristic parameter and the symmetry of the structure, which provides a flexible method of adjusting radiation directions. The directionality can be further improved by constructing a linear array. Our work establishes acoustic radiation control via quadrupolar metamaterials.

Automated summary

In this paper, we demonstrate the remarkable improvement in the directionality of acoustic radiation at low frequencies by using acoustic metamaterials arranged as an array of quadrupoles, compared with previous metamaterials arranged as monopole and dipole structures. The directivity can be adjusted by changing the characteristic parameter and symmetry of the structure, providing a flexible method of adjusting radiation directions. Furthermore, the directionality can be further improved by constructing a linear array. This work establishes the control of acoustic radiation via quadrupolar metamaterials.