The intensity of a wave emitted by a transducer affects its performance critically, especially when the emitted wave is omnidirectional. However, the development of omnidirectional transducers lags behind unidirectional ones, despite their practical usability in non-destructive testing. Here, we propose a metamaterial ring (“meta-ring”) enhancing the emission efficiency of omnidirectional SH elastic wave sources. Meta-ring is deliberately designed to follow the mechanical behavior of the discrete mass-spring model and is installed independently around the transducer. We interpret the involved physics for emission enhancement using homogenization and elucidate the two principles: a low impedance condition and a Fabry-Perot resonance. In addition, the two key design variables comprising the meta-ring are explored to modulate the practical adaptability. Experiments confirm that the meta-ring increased the emission efficiency of the transducer by over 250%. In that the intensity of an omnidirectional wave decreases inverse squarely in the two-dimensional space, the emission efficiency boosting by the proposed metamaterial concept can be critical in wide-area wave-based non-destructive evaluation.

换能器发射的波的强度对其性能有重要影响，尤其是当发射的波是全向的时。然而，全向换能器的发展落后于单向换能器，尽管它们在无损检测中具有实际可用性。在这里，我们提出了一种提高全向 SH 弹性波源发射效率的超材料环（“元环”）。Meta-ring 特意设计为遵循离散质量弹簧模型的机械行为，并独立安装在换能器周围。我们解释了使用均匀化增强发射所涉及的物理学，并阐明了两个原理：低阻抗条件和法布里-珀罗共振。此外，探索了构成元环的两个关键设计变量，以调节实际适应性。实验证实，元环将换能器的发射效率提高了 250% 以上。由于全向波的强度在二维空间中成反比地减小，因此所提出的超材料概念所提高的发射效率在基于广域波的无损评估中可能是至关重要的。