Enhancing plane-wave emission with a combination device based on acoustic metamaterial

Abstract

Generating high sound-intensity plane waves typically requires transducer arrays with complex synchronizing systems and high-output amplifiers. This work proposes a simple combination device to convert fan-shaped waves into elevated sound-pressure plane waves. The proposed device primarily relies on phase reconstruction of near-zero index metamaterials and the superposition of reflected waves in the reverberation field. The compact device, which is easy to manufacture, consists of a short waveguide equipped with two types of converters. One of the converters makes use of inverted cone's sound-guiding properties to convert fan-shaped waves into cylindrical waves over a broad frequency band. The other converter is comprised of rigid cylinders with triangular lattice arrays, effectively acting as the near-zero index metamaterial to transform cylindrical waves into plane waves. Both the simulated and experimental results show that the emitted plane waves can be linearly amplified by increasing the number of point sources that are separated by integer multiples of the wavelength in the vertical cavity. This study presents a straightforward and efficient approach to generate plane waves with a low-cost array assembly design, thereby enabling the widespread use of acoustic testing and underwater detection.