Acoustic Metal.
Mengyao Xie, Min Yang, Songwen Xiao, Yunfei Xu, Shuyu Chen · arXiv (Cornell University) · 2020
Metal reflects electromagnetic waves because of the large conductivity that is responsible for dissipation. During which the waves undergo a 180$^\circ$ phase change that is independent of the frequency. There is no counterpart material for waves. Here we show that by using an array of resonators with a designed high-density dissipative component, an acoustic can be realised that strongly couples with sound over a wide frequency range not otherwise attainable by conventional means. In particular, we show the Faraday cage effect that when used as a ring covering an air duct, 99% of the noise can be blocked without impeding the airflow. We further delineate the underlying volume requirement for an metal based on the constraint of the causality principle. Our findings complement the missing properties of materials and pave the way to the strong wave-material couplings that are critical for the applications as high-performance audio devices.