Acoustic absorbers at low frequency based on split-tube metamaterials

Highlights: • We propose a split-tube metamaterial absorber with a sensitive dependence on geometric parameters. • Simulation and experiment results confirm its high-efficiency and customizable absorptions. • Its compressive strength is theoretically analyzed and agreement with experimental measurement reveals its buckling behavior. • The metamaterial absorber has potential applications for noise reduction in both buildings and harsh environment. -- Abstract: The remarkable properties of acoustic metamaterials have attracted massive researches and applications, especially on low-frequency sound absorptions. Currently, most of the acoustic metamaterial absorbers employ resonances in plastic cavities, and their structural strengths are important in many circumstances, especially in harsh environment. However, studies of metamaterials including this point are very scarce. Here, we propose an acoustic metamaterial for low-frequency (<500 Hz) absorptions, composed of three nested square split tubes with inverted opening directions. The efficiency of the absorber is investigated both numerically and experimentally, and absorptions at the peeks are found to exceed 90% and the frequency can be effectively adjusted by tuning its geometric parameters. We further test its yield strength under compression and confirm its buckling behavior happens from the outmost layer. This tunable acoustic metamaterial with a fairly good mechanical strength may lead to broad applications in noise reduction.