Asymmetric Acoustic Energy Transport in Non-Hermitian Metamaterials

TL;DR

This paper introduces a novel non-Hermitian acoustic metamaterial that achieves asymmetric energy transport and switching with high frequency purity, overcoming limitations of traditional methods.

Contribution

It presents a unique design using spatially distributed linear and nonlinear losses to enable asymmetric acoustic transport without harmonic generation.

Findings

Demonstrates asymmetric acoustic reflectance and transmittance.

Achieves high frequency purity in outgoing signals.

Enables acoustic switching with low insertion loss.

Abstract

The ability to control and direct acoustic energy is essential for many engineering applications such as vibration and noise control, invisibility cloaking, acoustic sensing, energy harvesting, and phononic switching and rectification. The realization of acoustic regulators requires overcoming fundamental challenges inherent to the time-reversal nature of wave equations. Typically, this is achieved by utilizing either a parameter that is odd-symmetric under time-reversal or by introducing passive nonlinearities. The former approach is power consuming while the latter has two major deficiencies: it has high insertion losses and the outgoing signal is harvested in a different frequency than that of the incident wave due to harmonic generation. Here, we adopt a unique approach that exploits spatially distributed linear and nonlinear losses in a fork-shaped resonant metamaterial. Our compact design demonstrates asymmetric acoustic reflectance and transmittance, and acoustic switching. In contrast to previous studies, our non-Hermitian metamaterial exhibits asymmetric transport with high frequency purity of the outgoing signal.