Tapered rainbow metabeam for wideband multimode acoustic blocking based on quadruple-mode resonators

We construct a rainbow metamaterial for multimode sound blocking over a broad range of sub-kHz frequencies in the form of a tapered rectangular cross section beam of machined cells based on elements that can, on average, simultaneously attenuate the majority of the possible elastic-wave polarizations. Using aluminum, we construct a five-cell structure containing sub-wavelength planar resonators with interconnected ribs, which couple to compressional, in-plane shear, flexural, and torsional vibrations. Backed up by numerical simulations, we verify that this tapered structure can, on average, strongly attenuate acoustic modes over the frequency range of the combined metamaterial band gaps, that is over a frequency range representing -50% around -0.7 kHz. Applications include vibration isolation. Published under an exclusive license by AIP Publishing.

Automated summary

In this study, we constructed a rainbow metamaterial that can block multimode sound over a broad range of sub-kHz frequencies. The taperd rectangular cross section beam made of machined cells can attenuate various elastic-wave polarizations simultaneously. The numerical simulations confirmed the effectiveness of this structure in strongly attenuating acoustic modes over a frequency range representing -50% around -0.7 kHz. The applications of this metamaterial include vibration isolation.