Transformational acoustic metamaterials based on pressure gradients

TL;DR

This paper introduces a new approach to designing acoustic metamaterials using pressure gradients and the velocity potential equation, enabling advanced control like acoustic cloaking.

Contribution

It demonstrates that effective acoustic properties differ when derived from the velocity potential wave equation, offering a novel method for creating transformational acoustic devices.

Findings

Effective properties differ from pressure wave homogenization

Pressure gradients enable new acoustic metamaterial designs

Designed a device capable of acoustic velocity potential cloaking

Abstract

We apply a homogenization process to the acoustic velocity potential wave equation. The study of various examples shows that the resulting effective properties are different from those of the homogenized pressure wave equation for the same underlying acoustic parameters. A careful analysis reveals that a given set of inhomogeneous parameters represents an entirely different physical system depending on the considered equation. Our findings unveil a different way of tailoring acoustic properties through gradients of the static pressure. In contrast to standard metafluids based on isobaric composites, this alternative kind of metafluids is suitable for the implementation of transformational devices designed via the velocity potential equation. This includes acoustic systems in a moving background or arising from general space-time transformations. As an example, we design a device able to cloak the acoustic velocity potential.