Theory for tailoring sonic devices: Diffraction dominates over Refraction

TL;DR

This paper demonstrates that in acoustic crystal devices of several wavelengths, diffraction effects, especially edge diffraction, dominate over refraction, influencing device focusing and imaging capabilities.

Contribution

It provides the first evidence that diffraction, not refraction, governs the behavior of moderately long wavelength sonic devices, supported by FDTD simulations and experimental imaging.

Findings

Diffraction effects dominate over refraction in sonic devices of several wavelengths.

Edge diffraction plays a major role in device focusing and imaging.

Examples of sonic plane lens and acoustic prism demonstrate diffraction-controlled propagation.

Abstract

In the moderately long wavelength propagation regime, acoustic crystaldevices which size is of several wave lengths are studied by using thefinite-difference time domain method. It is shown by the focusing and imaging of a square shaped lens that the diffractive effects dominate over the refractive ones. Taking into account the well known Babinet principle, the major role of the device edge diffraction is shown. The first examples of imaging with a sonic plane lens and of an acoustic prism able to change the propagation direction of a plane wave are also presented here.