Lightweight membrane-type acoustic metamaterials with through-holes

Membrane-type acoustic metamaterials with attached small masses have been reported to break the classical mass law on traditional acoustic materials and can effectively insulate low-frequency noises. In this work, we propose lightweight membrane-type acoustic metamaterials with through Our acoustic metamaterials yield high transmission loss (TL) at selective frequencies below 1st eigenfrequency frequency regime (<1000 Hz). The varying the through-hole microphones impedance tube measurements agree results. The acoustic near membrane were experimentally visualized with sound intensity measurements, and numerically calculated. These analyses indicate that the mechanism of the high TL is based on the destructive interference between two types of acoustic near-fields generated from vibration sound of the membrane. The proposed design has promising potentials as a new type of thin and lightweight noise control devices with air-flow.