Acoustic Wavefront Shaping Using Ultrahigh Phase Resolution Metamaterial

Abstract Acoustic wavefront shaping through metamaterials by engineering their phase and amplitude at a subwavelength scale has gained substantial interest in acoustic lensing, acoustic imaging, and noise control with ventilation. However, current metamaterials generally capable of wavefront manipulation rely on complex geometries with limited phase resolution and require a library of multiple metamaterial bricks. Here, a new transmissive metamaterial unit cell composed of a subwavelength Bilateral Symmetrical T‐shaped (BST) structure placed within a rectangular waveguide is proposed. The simple design of the BST structure and its rotation along the z ‐axis within the rectangular waveguide gives precise control over phase delay upto π/36 radian resolution for sound waves at a frequency of 8000 Hz. Experiments, simulations, and theoretical modelling are done on the BST structure unit cell to define the underlying causes of the observed phase delays. Finally, the designed unit cell is fabricated as a full‐scale metamaterial composed of 17 × 17 units using polyjet 3D printing and analysed for sound focusing and steering functionalities, validating the results through experiments and numerical simulations. The design of the unit cell exhibits high phase resolution, enabling opportunities to construct novel acoustic devices with multiple