We propose a novel method to boost the power of a magnetostrictive patch transducer (MPT) for generating antisymmetric Lamb wave modes in a plate. Because an MPT installed on a plate mainly exerts in-plane deformation onto a test specimen, it cannot efficiently generate antisymmetric wave modes such as the lowest antisymmetric Lamb wave ( A ₀ ) mode, unlike the generation of symmetric wave modes. To achieve the high-power generation of antisymmetric modes, we propose an add-on passive boosting element which is referred to here as a detuned resonator. The resulting MPT can serve both as an actuator and a sensor. Here, we present the specific boosting resonator configuration, explain its operating mechanism, and verify its role in increasing the transducer power. A theoretical analysis and experimental validation are carried out.

This study explores tunable sound absorption using a bilayer configuration of phase‐gradient acoustic metasurfaces. By carefully adjusting the cavity length between two metasurface layers, the proposed system can modulate its acoustic response between highly reflective and perfectly absorptive states without changing the internal geometry of the unit cells. The underlying mechanism results from evanescent‐wave coupling, which becomes significant at sub‐wavelength cavity length and is strongly influenced by the phase gradient and integer parity of each metasurface. To analyze the scattering behavior of the bilayer system, an analytical model based on coupled‐mode theory is developed, identifying the conditions that ensure both reflection and transmission are effectively suppressed. Theoretical predictions are validated by full‐wave simulations using bilayer metasurfaces realized with space‐coiling structures. The results demonstrate broadband tunability in sound absorption, with optimal configurations achieving an absorption coefficient exceeding 95%. Owing to its structural simplicity and high tunability, the proposed approach offers an effective solution for dynamic sound control in applications such as tunable noise barriers and reconfigurable sound‐absorbing devices.