A core challenge of acoustically optimizing an automotive sound system is realizing a balance between ideal and viable loudspeaker placement. Placement is largely influenced by structural, aesthetic and safety design considerations leading to non-ideal acoustic response characteristics within a given car cabin. These constrains often force drive units to be oriented off-axis from the listening region. To fully benefit from a transducer’s performance, the on-axis response is desirable at the listening location. This work presents the design and evaluation of design of broadband acoustic meta-material lenses to perform beam steering on an incoming wavefront. The parameters of the meta-material lens are learned via a differentiable acoustic simulation, evaluating the far-field directivity of the lens by solving the inhomogeneous Helmholtz equation via Fourier spectral methods coupled with a far field approximation of the boundary integral method. To realise a physical lens from the theoretical lens, a differential evolutionary algorithm is used to optimize the geometry of a parametric 2D model for each element of the metamaterial lens’s cross-section, matching the target effective density and bulk modulus via Finite Element Method (FEM) analysis. The performance of the whole lens is then evaluated via FEM analysis. After this, resin 3D printing is used to construct the metamaterial lens which is used to verify the results in real world.
