Enhancement of sound in chirped sonic crystals

TL;DR

This paper introduces a new method for concentrating sound waves in chirped sonic crystals, achieving significant energy enhancement through controlled slow-down of sound at specific planes, with potential applications to other wave types.

Contribution

The study presents a novel mechanism of sound concentration in chirped sonic crystals, supported by experimental demonstration and a simple coupled mode theory.

Findings

Energy concentration up to 20 times at bright planes

Effective for frequencies near the first band gap

Applicable to other wave types in modulated media

Abstract

We propose and experimentally demonstrate a novel mechanism of sound wave concentration based on soft reflections in chirped sonic crystals. The reported controlled field enhancement occurs at around particular (bright) planes in the crystal, and is related to a progressive slowing down of the sound wave as it propagates along the material. At these bright planes, a substantial concentration of the energy (with a local increase up to 20 times) was obtained for a linear chirp and for frequencies around the first band gap. A simple couple mode theory is proposed, that interprets and estimates the observed effects. The results are obtained for the case of sound waves and sonic crystals, however they are extendable to other type of waves in modulated host matter.