Simultaneous acoustic perfect absorption and rainbow trapping via topologically optimized sub-wavelength multi-slit sonic crystal metamaterials

Abstract

Acoustic perfect absorption at 500 Hz and across the low-frequency range of 400–1000 Hz is demonstrated using a metamaterial structure composed of graded sub-wavelength multi-slit sonic crystal (MSSC) elements designed through a topology optimization framework that integrates a genetic algorithm with a novel effective medium approach, rigorously accounting for visco-thermal losses in the slits via Stinson’s model, avoiding reliance on artificial loss factors. The effective impedances of the unit cells embedding each MSSC element are precisely tuned to match the surrounding medium, thereby satisfying the critical coupling condition for optimal absorption. Remarkably, the optimized structure exhibits spatially graded acoustic properties that sequentially localize energy at designated frequencies, producing the rainbow-trapping phenomenon. Notably, the largest element measures only 7 cm in diameter—deeply sub-wavelength at about 1/12 the wavelength at 400 Hz. The proposed design and methodology offer promising applications in acoustic filtering, energy harvesting, and noise mitigation, particularly in ventilation systems.

Metadata

Item Type:	Article
Authors/Creators:	Lam, W.K. Krynkin, A. https://orcid.org/0000-0002-8495-691X Umnova, O. Tang, S.K.
Copyright, Publisher and Additional Information:	© The Author(s) 2025. Open Access: This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Keywords:	Acoustics; Mechanical engineering
Dates:	Accepted: 23 August 2025 Published (online): 8 January 2026 Published: 8 January 2026
Institution:	The University of Sheffield
Academic Units:	The University of Sheffield > Faculty of Engineering (Sheffield) > School of Mechanical, Aerospace and Civil Engineering
Date Deposited:	27 Jan 2026 17:06
Last Modified:	27 Jan 2026 17:06
Status:	Published
Publisher:	Springer Science and Business Media LLC
Refereed:	Yes
Identification Number:	10.1038/s44384-025-00026-5
Sustainable Development Goals:
Open Archives Initiative ID (OAI ID):	oai:eprints.whiterose.ac.uk:236901

Download

Published Version

Filename: s44384-025-00026-5.pdf

Licence: CC-BY-NC-ND 4.0

CLICK TO DOWNLOAD

CORE (COnnecting REpositories)

Simultaneous acoustic perfect absorption and rainbow trapping via topologically optimized sub-wavelength multi-slit sonic crystal metamaterials

Abstract

Metadata

Download

Published Version

Export

Statistics