A Nonlinear Gradient-Coiling Metamaterial for Enhanced Acoustic Signal Sensing

Abstract

Acoustic sensing systems play a critical role in identifying and determining weak sound sources in various fields. In many fault warning and environmental monitoring processes, sound-based sensing techniques are highly valued for their information-rich and non-contact advantages. However, noise signals from the environment reduce the signal-to-noise ratio (SNR) of conventional acoustic sensing systems. Therefore, we proposed novel nonlinear gradient-coiling metamaterials (NGCMs) to sense weak effective signals from complex environments using the strong wave compression effect coupled with the equivalent medium mechanism. Theoretical derivations and finite element simulations of NGCMs were executed to verify the properties of the designed metamaterials. Compared with nonlinear gradient acoustic metamaterials (Nonlinear-GAMs) without coiling structures, NGCMs exhibit far superior performance in terms of acoustic enhancement, and the structures capture lower frequencies and possess a wider angle acoustic response. Additionally, experiments were constructed and conducted using set Gaussian pulse and harmonic acoustic signals as emission sources to simulate real application scenarios. It is unanimously shown that NGCMs have unique advantages and broad application prospects in the application of weak acoustic signal sensing, enhancement and localization.

Broadband acoustic signal enhancement via gradient metamaterials coupled to crystals

“…Accordingly, we build a 2D structure within the acoustic module (pressure acoustics and thermoviscous acoustics) of COMSOL Multiphysics v6.0, as illustrated in Figure 1C, with the point probe positions set at the locations marked in red (16th, 19th, 22nd, and 25th air gaps). The pressure gain value (PG) is an important indicator of the acoustic enhancement effect, defined as PG = PM/PF [28,38]. PM denotes the sound pressure amplitude added to the metamaterial structure, while PF indicates the sound pressure amplitude in the free sound field.…”