Reciprocity is a fundamental principle in acoustics, posing constraints on the way we process acoustic signals. Breaking reciprocity with spatiotemporal modulations provides an opportunity to design compact, low-energy, integrated non-reciprocal acoustic devices. Here, we design and experimentally demonstrate a space-time modulated programmable metamaterial beam with electromagnet resonators controlled by currents. A numerical approach based on the finite element method is developed for wave dispersion calculations of space-time modulated programmable metamaterials with complex geometries. Unidirectional band gaps are demonstrated experimentally and numerically in a good agreement. We quantify effects of the modulation amplitude and material damping in terms of band gap width and attenuation factor of the unidirectional band gaps in the space-time modulated metamaterial beam. Lastly, the unidirectional band gaps due to the second-order mode coupling caused by strong modulations are identified and examined numerically. Our design as well as the numerical approach provide a practical solution for the applications of non-reciprocal acoustic devices with spatiotemporal modulations.

Date Published: 1 April 2019
PDF
Proc. SPIE 10972, Health Monitoring of Structural and Biological Systems XIII, 109720F (1 April 2019); doi: 10.1117/12.2514165

Published in SPIE Proceedings Vol. 10972:
Health Monitoring of Structural and Biological Systems XIII
Paul Fromme; Zhongqing Su, Editor(s)