Lightweight architected hollow sphere foams for simultaneous noise and vibration control

Phononic metamaterials, composed of periodically topological structures and materials dispersions, can manipulate acoustic or elastic wave propagation, but not concurrently in most cases. Here we report a new type of three-dimensional (3D) architected hollow sphere foams that can attenuate acoustic and elastic waves synchronically. Our numerical simulation results reveal that the acoustic wave attenuation is attributed to local resonances in the drilled hollow spheres, which act as Helmholtz resonators. The elastic wave mitigation stems from Bragg scatterings in the 3D architected periodic hollow sphere foams. The numerically predicted acoustic and elastic wave band gaps are further validated against the corresponding transmission spectra, which are obtained by performing frequency domain analysis. Notably, elastic wave band gap properties can be decoupled from acoustic wave and independently tuned by tailoring the connectivity among the hollow spheres. The findings reported here offer new opportunities to design lightweight architected metamaterials to simultaneously control undesired noise and vibration over a wide frequency range.