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Acoustic Properties of Materials
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Acoustic Properties of Materials

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Physics".

Deadline for manuscript submissions: closed (20 November 2022) | Viewed by 9093

Special Issue Editor

Prof. Dr. Fengxian Xin

E-Mail Website
Guest Editor
School of Aerospace, Xi'an Jiaotong University, Xi'an, China
Interests: mechanics of soft materials; acoustics of porous materials and structures

Special Issue Information

Dear Colleagues,

Acoustic properties are important solid physical characteristics of materials. The acoustic properties of materials have a close relationship with their structures, especially for porous materials or composite materials. By studying acoustic properties like the sound absorption coefficient (SAC) and sound transmission loss (STL) of materials with different frequencies, the effects of the internal structural information (e.g., porosity, filling shapes, fiber diameter, fiber content, and shape of air layer) can be further understood.

The study of the acoustic properties of materials has many applications. For example, from comparative analyses of experimental results and theoretical models, researchers may determine empirical functions between structural characteristic parameters and explore further applications of these functions, such as the nondestructive testing of composites and the evaluation of textiles. The vibration of heavy equipment and its noise control have also gained increasing attention from researchers of various research backgrounds (material science, mechanical engineering, sustainability, applied physics, etc.).

We welcome the submission of original theoretical or experimental papers contributing to furthering the knowledge in wave mechanics; the acoustic properties of porous materials; material structure vibration and noise control; lightweight material structure vibration and noise reduction; the design, performance characterization, and application of metamaterials or meta structures; and the structural mechanics, vibration, and noise reduction of composite materials.

Prof. Dr. Fengxian Xin
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • wave mechanics
  • acoustic properties of porous materials
  • material structure vibration and noise control
  • lightweight material structure vibration and noise reduction
  • design, performance characterization, and application of metamaterials or meta structures
  • structural mechanics, vibration, and noise reduction of composite materials

Published Papers (4 papers)

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Research

16 pages, 7644 KiB  
Article
Acoustic Performance of Stress Gradient-Induced Deflection of Triangular Unimorphic/Bimorphic Cantilevers for MEMS Applications
by Ning-Hsiu Yuan, Chih-Chia Chen, Yiin-Kuen Fuh and Tomi T. Li
Materials 2023, 16(5), 2129; https://doi.org/10.3390/ma16052129 - 06 Mar 2023
Viewed by 1457
Abstract
This paper reports two piezoelectric materials of lead zirconium titanate (PZT) and aluminum nitride (AlN) used to simulate microelectromechanical system (MEMS) speakers, which inevitably suffered deflections as induced via the stress gradient during the fabrication processes. The main issue is the vibrated deflection [...] Read more.
This paper reports two piezoelectric materials of lead zirconium titanate (PZT) and aluminum nitride (AlN) used to simulate microelectromechanical system (MEMS) speakers, which inevitably suffered deflections as induced via the stress gradient during the fabrication processes. The main issue is the vibrated deflection from the diaphragm that influences the sound pressure level (SPL) of MEMS speakers. To comprehend the correlation between the geometry of the diaphragm and vibration deflection in cantilevers with the same condition of activated voltage and frequency, we compared four types of geometries of cantilevers including square, hexagon, octagon, and decagon in triangular membranes with unimorphic and bimorphic composition by utilizing finite element method (FEM) for physical and structural analyses. The size of different geometric speakers did not exceed 10.39 mm2; the simulation results reveal that under the same condition of activated voltage, the associated acoustic performance, such as SPL for AlN, is in good comparison with the simulation results of the published literature. These FEM simulation results of different types of cantilever geometries provide a methodology design toward practical applications of piezoelectric MEMS speakers in the acoustic performance of stress gradient-induced deflection in triangular bimorphic membranes. Full article
(This article belongs to the Special Issue Acoustic Properties of Materials)
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13 pages, 4873 KiB  
Article
Acoustic Assessment of Multiscale Porous Lime-Cement Mortars
by Irene Palomar and Gonzalo Barluenga
Materials 2023, 16(1), 322; https://doi.org/10.3390/ma16010322 - 29 Dec 2022
Viewed by 1169
Abstract
Noise pollution is an issue of high concern in urban environments and current standards and regulations trend to increase acoustic insulation requirements concerning airborne noise control. The design and development of novel building materials with enhanced acoustic performance is an efficient solution to [...] Read more.
Noise pollution is an issue of high concern in urban environments and current standards and regulations trend to increase acoustic insulation requirements concerning airborne noise control. The design and development of novel building materials with enhanced acoustic performance is an efficient solution to mitigate this problem. Their application as renders and plasters can improve the acoustic conditions of existing and brand-new buildings. This paper reports the acoustic performance of eleven multiscale porous lime-cement mortars (MP-LCM) with two types of fibers (cellulose and polypropylene), gap-graded sand, and three lightweight aggregates (expanded clay, perlite, and vermiculite). Gap-graded sand was replaced by 25 and 50% of lightweight aggregates. A volume of 1.5% and 3% of cellulose fibers were added. The experimental study involved a physical characterization of properties related to mortar porous microstructure, such as apparent density, open porosity accessible to water, capillarity absorption, and water vapor permeability. Mechanical properties, such as Young’s modulus, compressibility modulus, and Poisson’s ratio were evaluated with ultrasonic pulse transmission tests. Acoustic properties, such as acoustic absorption coefficient and global index of airborne noise transmission, were measured using reduced-scale laboratory tests. The influence of mortar composition and the effects of mass, homogeneity, and stiffness on acoustic properties was assessed. Mortars with lower density, lower vapor permeability, larger open porosity, and higher Young’s and compressibility modulus showed an increase in sound insulation. The incorporation of lightweight aggregates increased sound insulation by up to 38% compared to the gap-graded sand reference mixture. Fibers slightly improved sound insulation, although a small fraction of cellulose fibers can quadruplicate noise absorption. The roughness of the exposed surface also affected sound transmission loss. A semi-quantitative multiscale model for acoustic performance, considering paste thickness, active void size, and connectivity of paste pores as key parameters, was proposed. It was observed that MP-LCM with enhanced sound insulation, slightly reduced sound absorption. Full article
(This article belongs to the Special Issue Acoustic Properties of Materials)
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15 pages, 4409 KiB  
Article
Investigation of the Underwater Absorption and Reflection Characteristics by Using a Double-Layer Composite Metamaterial
by Yi Zhu, Xinyang Zhao, Zhiyuan Mei, Haitao Li and Dajiang Wu
Materials 2023, 16(1), 49; https://doi.org/10.3390/ma16010049 - 21 Dec 2022
Cited by 3 | Viewed by 1958
Abstract
It is well-known that the acoustic stealth of an underwater vehicle composed of a non-watertight structure has been facing severe challenges. The origins of this effect are associated with the fact that the coupling between the water and the mechanical structure is not [...] Read more.
It is well-known that the acoustic stealth of an underwater vehicle composed of a non-watertight structure has been facing severe challenges. The origins of this effect are associated with the fact that the coupling between the water and the mechanical structure is not negligible because both sides are in the water. Along these lines, the idea of forward absorption and backward reflection was proposed in this work to address this issue. More specifically, a composite underwater acoustic metamaterial (AM) was designed based on different layers, namely a sound absorption layer and a sound insulation layer from the outside to the inside. The sound absorption layer was made of a soft rubber matrix with embedded steel scatterers (ESs) to enrich the coupled resonance effects, while the sound insulation layer was composed of hard rubber with a built-in cavity to improve the impedance mismatching between the AM and the water. The impact of the number and thickness of the embedded ESs on the acoustic performance of the AM was also thoroughly investigated via a finite element method (FEM). A fast non-dominated genetic algorithm (NAGA-II) with elite strategy was used to optimize the position and the size of the ESs. The optimization results revealed the high absorption at the forward incidence and the high reflection at the backward incidence. Thus, our work provides a novel and effective approach for improving the acoustic stealth of underwater vehicles composed of non-watertight structures. Full article
(This article belongs to the Special Issue Acoustic Properties of Materials)
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16 pages, 2616 KiB  
Article
Acoustic Metamaterials for Low-Frequency Noise Reduction Based on Parallel Connection of Multiple Spiral Chambers
by Haiqin Duan, Fei Yang, Xinmin Shen, Qin Yin, Enshuai Wang, Xiaonan Zhang, Xiaocui Yang, Cheng Shen and Wenqiang Peng
Materials 2022, 15(11), 3882; https://doi.org/10.3390/ma15113882 - 29 May 2022
Cited by 15 | Viewed by 2581
Abstract
Acoustic metamaterials based on Helmholtz resonance have perfect sound absorption characteristics with the subwavelength size, but the absorption bandwidth is narrow, which limits the practical applications for noise control with broadband. On the basis of the Fabry–Perot resonance principle, a novel sound absorber [...] Read more.
Acoustic metamaterials based on Helmholtz resonance have perfect sound absorption characteristics with the subwavelength size, but the absorption bandwidth is narrow, which limits the practical applications for noise control with broadband. On the basis of the Fabry–Perot resonance principle, a novel sound absorber of the acoustic metamaterial by parallel connection of the multiple spiral chambers (abbreviated as MSC-AM) is proposed and investigated in this research. Through the theoretical modeling, finite element simulation, sample preparation and experimental validation, the effectiveness and practicability of the MSC-AM are verified. Actual sound absorption coefficients of the MSC-AM in the frequency range of 360–680 Hz (with the bandwidth Δf1 = 320 Hz) are larger than 0.8, which exhibit the extraordinarily low-frequency sound absorption performance. Moreover, actual sound absorption coefficients are above 0.5 in the 350–1600 Hz range (with a bandwidth Δf2 = 1250 Hz), which achieve broadband sound absorption in the low–middle frequency range. According to various actual demands, the structural parameters can be adjusted flexibly to realize the customization of sound absorption bandwidth, which provides a novel way to design and improve acoustic metamaterials to reduce the noise with various frequency bands and has promising prospects of application in low-frequency sound absorption. Full article
(This article belongs to the Special Issue Acoustic Properties of Materials)
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