Comment on "Design of acoustic devices with isotropic material via conformal transformation" [Appl. Phys. Lett. 97, 044101 (2010)]

TL;DR

This paper critiques a previous work on acoustic device design, highlighting errors in the formulas for density and bulk modulus caused by incorrect assumptions about acoustic impedance.

Contribution

It identifies and clarifies the inaccuracies in the formulas used in the prior study, emphasizing the importance of correct impedance assumptions in conformal transformations.

Findings

Incorrect formulas for density and bulk modulus identified

Highlighting the impact of impedance assumptions on acoustic device design

Clarification of proper conformal transformation application

Abstract

The paper presents incorrect formulas for the density and bulk modulus under a conformal transformation of coordinates. The fault lies with an improper assumption of constant acoustic impedance.