An ultralight phononic beam with a broad low-frequency band gap using the complex lattice of acoustic black holes

An ultralight phononic beam (PB) using the complex lattice of acoustic black holes (ABHs) is designed for producing broad low-frequency band gaps (BGs). Its unit-cell contains in-series outward-and-inward-curved ABHs and is over one-third lighter than its simple-lattice counterparts. Ultrawide low-frequency BGs are achieved due to multi-modal and complex-modal behaviors and the reduced structure stiffness by extra ABH introduced in the unit-cell. The BGs are tunable to lower and broader frequencies by adjusting the residue thickness of each ABH. Furthermore, broad low-frequency vibration attenuations of the finite-size PB are investigated and experimentally verified. Our approach allows broadband low-frequency vibration control by using an ultralight structure.