Adjustable Sound Absorber of Multiple Parallel-Connection Helmholtz Resonators with Tunable Apertures Prepared by Low-Force Stereolithography of Photopolymer Resin.

Content Provider	Europe PMC
Author	Yang, Fei Bi, Shaohua Shen, Xinmin Li, Zhizhong Zhang, Xiangpo Wang, Enshuai Yang, Xiaocui Peng, Wenqiang Huang, Changchuang Liang, Peng Sun, Guoxin
Editor	Neipp, Cristian
Copyright Year	2022
Abstract	The variable noise spectrum for many actual application scenarios requires a sound absorber to adapt to this variation. An adjustable sound absorber of multiple parallel-connection Helmholtz resonators with tunable apertures (TA–MPCHRs) is prepared by the low-force stereolithography of photopolymer resin, which aims to improve the applicability of the proposed sound absorber for noise with various frequency ranges. The proposed TA–MPCHR metamaterial contains five metamaterial cells. Each metamaterial cell contains nine single Helmholtz resonators. It is treated as a basic structural unit for an array arrangement. The tunable aperture is realized by utilizing four segments of extendable cylindrical chambers with length l0, which indicates that the length of the aperture l is in the range of [l0, 4l0], and that it is tunable. With a certain group of specific parameters for the proposed TA–MPCHR, the influence of the tunable aperture with a variable length is investigated by acoustic finite element simulation with a two-dimensional rotational symmetric model. For the given noise spectrum of certain actual equipment with four operating modes, the TA–MPCHR sample with a limited total thickness of 40 mm is optimized, which is made of photopolymer resin by the low-force stereolithography, and its actual average sound absorption coefficients for the frequency ranges of 500–800 Hz, 550–900 Hz, 600–1000 Hz and 700–1150 Hz reach 0.9203, 0.9202, 0.9436 and 0.9561, respectively. Relative to common non-adjustable metamaterials, the TA–MPCHR made of photopolymer resin can reduce occupied space and improve absorption efficiency, which is favorable in promoting its practical applications in the noise pollution prevention.
Journal	Polymers
Volume Number	14
PubMed Central reference number	PMC9786290
Issue Number	24
PubMed reference number	36559802
e-ISSN	20734360
DOI	10.3390/polym14245434
Language	English
Publisher	MDPI
Publisher Date	2022-12-12
Access Restriction	Open
Rights License	Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). © 2022 by the authors.
Subject Keyword	adjustable acoustic metamaterials TA–MPCHR sound absorption performance photopolymer resin low-force stereolithography acoustic finite element simulation various noise control
Content Type	Text
Resource Type	Article
Subject	Chemistry Polymers and Plastics