Passive underwater acoustic barcodes using Rayleigh wave resonance

Abstract

Passive underwater acoustic markers are promising in terms of applications in underwater target recognition, positioning, and navigation. In this paper, a passive underwater acoustic marker composed of acrylic sphere combinations is designed for acoustic coding based on the subsonic Rayleigh wave resonance phenomenon, where strong backscattering resonance peaks appear when an acrylic sphere is excited by a broadband pulse. Due to the fact that the resonance frequencies are dependent on the Rayleigh wave velocity and the radius of the sphere, the backscattering response of markers can be regulated by changing the radius of a sphere or combining spheres with different radii. Each marker has a unique acoustic signature for a selected frequency band, akin to acoustic barcodes. The feasibility of this acoustic coding method has been evaluated by comparing the numerical results and experimental results. Compared with active acoustic markers, passive acoustic markers naturally operate in a wider frequency band, have a longer lifetime, and lower cost.