Sound directivity control in piezoelectric metamaterial plates via mode tailoring

Smart metamaterials with adaptive architectures offer potential for the manipulation of elastic and acoustic waves. This study investigates a metamaterial plate designed for tunable sound directivity control via an array of piezoelectric unit cells shunted by inductive circuits. By adjusting the inductance values to tune the resonance of the shunted piezoelectric unit cells, the local structural impedance of the plate is tailored, enabling active reconfiguration of its global dynamic behavior. We develop an analytical framework for designing vibration modes and validate the approach using a combination of finite element simulations and experimental measurements. The results demonstrate that by strategically tailoring the shunt circuit parameters of each unit cell, specific vibration modes can be enforced at a desired operating frequency. The high correlation between numerical predictions and experimental results for out-of-plane velocity and the acoustic near-field confirms that sound radiation patterns can be effectively steered, providing a robust mechanism for programmable acoustic wave manipulation.