Experimental Realization of Acoustic Bianisotropic Gratings

TL;DR

This paper demonstrates the design, fabrication, and experimental validation of acoustic gratings that exhibit bianisotropic properties, enabling asymmetric sound wave transmission and reflection through optimized unit cell structures.

Contribution

It introduces a systematic method to realize acoustic bianisotropic coupling using optimized gratings with broken symmetry, validated by experiments.

Findings

Achieved asymmetric wave scattering in airborne sound.

Validated design through experimental measurements.

Matched experimental results with theoretical predictions.

Abstract

Acoustic bianisotropic materials couple pressure and local particle velocity fields to simultaneously excite monopole and dipole scattering, which results in asymmetric wave transmission and reflection of airborne sound. In this work, we systematically realize an arbitrarily given bianisotropic coupling between the pressure and velocity fields for asymmetric wave propagation by an acoustic grating with inversion symmetry breaking. This acoustic bianisotropic grating is designed by optimizing the unit cells with a finite element method to achieve the desired scattering wavevectors determined by the bianisotropic induced asymmetric wave propagation. The symmetry and Bloch wavevectors in the reciprocal space resulted from the grating are analyzed, which match with the desired scattering wavevectors. The designed structures are fabricated for the experimental demonstration of the bianisotropic properties. The measured results match with the desired asymmetric wave scattering fields.