A hybrid acoustic metamaterial for low-frequency constant nearly perfect sound absorption with large deformation

The sound absorption capacity of cavity-based absorbers is inevitably severely affected by structural deformation due to external loads, and dynamic tunability of the absorption frequency cannot be achieved once fabrication is complete. In this work, a novel compressible hybrid metamaterial for low-frequency constant sound absorption is proposed, which ingeniously combines the characteristics of origami-inspired V-shaped and helical structures, integrating a Helmholtz resonator with two extended necks and a micro-perforated panel resonator. The metamaterial is manufactured using 3D printing technology. Experimental and analytical results demonstrate that the nearly perfect sound absorption is constantly maintained at 315 Hz no matter how the absorber deforms, while the second absorption peak can be tuned from 509 Hz to 682 Hz with a compression strain range of 0 % to 31.3 %. The absorber also exhibits excellent absorption at oblique incidence angles up to 60 degrees, both before and after deformation. Moreover, by employing a coupled unit strategy the low-frequency absorption bandwidth can be broadened, while maintaining stability within the range of 316-391 Hz during structural deformation. This design strategy provides a promising approach for enabling adaptive sound absorption and multifunctional metamaterials, opening up new possibilities for tunable noise control applications.