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Innovative Composite Materials for Sound Absorption and Insulation

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

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 39998

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Prof. Dr. Francesco Martellotta

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Dipartimento di Architettura Costruzione e Design, Politecnico di Bari, Via Orabona n.4, 70125 Bari, Italy
Interests: hermal comfort; indoor environment quality; architectural acoustics; building simulation; energy saving and renewable energies
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Dear Colleagues,

In recent years we have observed a growing interest in sound absorption and sound insulation as a consequence of the ever-increasing awareness of the adverse effects that noise and lack of acoustic comfort may have on human health. Such an interest consequently stimulated researchers (and industry) to propose new materials with improved characteristics. For sound absorbing materials it is important to combine a sufficiently wide frequency range of action, with reduced mass and thickness, as well as with aesthetic requirements (due to the need to use such materials in spaces like classrooms, restaurants, train stations, etc.), not to mention durability and ease of maintenance. For sound insulating materials aesthetic problems are typically not an issue, but other aspects, such as balancing low dynamic stiffness with load bearing properties, become important in order to ensure the best performance. In addition, whatever the purpose, such devices should be sustainable, have a low impact in terms of life cycle assessment, and possibly involve the use of recycled materials or natural products. All of the above questions clearly represent a challenge for researchers, but at the same time they offer new opportunities to experiment with cutting-edge solutions, like those based on the use of composite materials, also including nanotechnologies, “green” vegetal and animal fibers, metal/ceramic/polymer matrixes, or even the more “advanced” acoustic metamaterials. At the same time, new, or updated, mathematical models and simulation tools will be needed to explain and predict the acoustic behavior of such composite materials.

This Special Issue provides an excellent opportunity for those who are studying and working within this continuously evolving field. Research articles, review articles and communications relating to theory, simulation, fabrication, properties characterization and applications of sound-absorbing and sound-insulating composite materials are all invited for this Special Issue.

Prof. Francesco Martellotta
Guest Editor

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Keywords

Sound-absorbing materials
Sound-insulating materials
Composite materials
Sustainable and green materials

Published Papers (12 papers)

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Editorial

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3 pages, 173 KiB

Open AccessEditorial

Innovative Composite Materials for Sound Absorption and Insulation: Where We Are and Where We Are Going

by Francesco Martellotta

Materials 2021, 14(8), 1954; https://doi.org/10.3390/ma14081954 - 14 Apr 2021

Cited by 2 | Viewed by 1681

Abstract

Materials with sound-absorbing or sound-insulating properties have been rapidly evolving in recent years due to several reasons [...] Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

Research

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20 pages, 5763 KiB

Open AccessArticle

Performance Characterization of Broad Band Sustainable Sound Absorbers Made of Almond Skins

by Stefania Liuzzi, Chiara Rubino, Pietro Stefanizzi and Francesco Martellotta

Materials 2020, 13(23), 5474; https://doi.org/10.3390/ma13235474 - 01 Dec 2020

Cited by 18 | Viewed by 1972

Abstract

In order to limit the environmental impact caused by the use of non-renewable resources, a growing research interest is currently being shown in the reuse of agricultural by-products as new raw materials for green building panels. Moreover, the European directives impose the goal of sustainability supporting the investigation of passive solutions for the reduction of energy consumption. Thus, the promotion of innovative building materials for the enhancement of acoustic and thermal insulation of the buildings is an important issue. The aim of the present research was to evaluate the physical, acoustical, and thermal performances of building panels produced by almond skin residues, derived from the industrial processing of almonds. In this paper different mix designs were investigated using polyvinyl acetate glue and gum Arabic solution as binders. Air-flow resistivity σ and normal incidence sound absorption coefficient α were measured by means of a standing wave tube. Thermal conductivity λ, thermal diffusivity α, volumetric heat capacity ρc were measured using a transient plane source device. Finally, water vapor permeability δ_p was experimentally determined using the dry cup method. Furthermore, a physical characterization of the specimens in terms of bulk density ρ_b and porosity η allowed to study the correlation existing between the binder and the aggregates and the consequent acoustical and hygrothermal behavior occurring on the different mix designs. The achieved results suggested the investigated materials comparable to the main products currently existing on the market. Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

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19 pages, 1966 KiB

Open AccessArticle

Graded and Anisotropic Porous Materials for Broadband and Angular Maximal Acoustic Absorption

by Théo Cavalieri, Jean Boulvert, Gwénaël Gabard, Vicent Romero-García, Marie Escouflaire, Josselin Regnard and Jean-Philippe Groby

Materials 2020, 13(20), 4605; https://doi.org/10.3390/ma13204605 - 16 Oct 2020

Cited by 13 | Viewed by 2447

Abstract

The design of graded and anisotropic materials has been of significant interest, especially for sound absorption purposes. Together with the rise of additive manufacturing techniques, new possibilities are emerging from engineered porous micro-structures. In this work, we present a theoretical and numerical study of graded and anisotropic porous materials, for optimal broadband and angular absorption. Through a parametric study, the effective acoustic and geometric parameters of homogenized anisotropic unit cells constitute a database in which the optimal anisotropic and graded material will be searched for. We develop an optimization technique based on the simplex method that is relying on this database. The concepts of average absorption and diffuse field absorption coefficients are introduced and used to maximize angular acoustic absorption. Numerical results present the optimized absorption of the designed anisotropic and graded porous materials for different acoustic targets. The designed materials have anisotropic and graded effective properties, which enhance its sound absorption capabilities. While the anisotropy largely enhances the diffuse field absorbing when optimized at a single frequency, graded properties appear to be crucial for optimal broadband diffuse field absorption. Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

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10 pages, 2698 KiB

Open AccessArticle

Sound Transmission Loss of a Sandwich Plate with Adjustable Core Layer Thickness

by Tom Ehrig, Martin Dannemann, Ron Luft, Christian Adams, Niels Modler and Pawel Kostka

Materials 2020, 13(18), 4160; https://doi.org/10.3390/ma13184160 - 18 Sep 2020

Cited by 6 | Viewed by 2804

Abstract

Compressible Constrained Layer Damping (CCLD) is a novel, semi-active, lightweight-compatible solution for vibration mitigation based on the well-known constrained layer damping principle. The sandwich-like CCLD set-up consists of a base structure, a constraining plate, and a compressible open-cell foam core in between, enabling the adjustment of the structure’s vibration behaviour by changing the core compression using different actuation pressures. The aim of the contribution is to show to what degree, and in which frequency range the acoustic behaviour can be tuned using CCLD. Therefore, the sound transmission loss (TL), as an important vibro-acoustic index, is determined in an acoustic window test stand at different actuation pressures covering a frequency range from 0.5 to 5 kHz. The different actuation pressures applied cause a variation of the core layer thickness (from 0.9 d₀ to 0.3 d₀), but the resulting changes of the stiffness and damping of the overall structure have no significant influence on the TL up to approximately 1 kHz for the analysed CCLD design. Between 1 kHz and 5 kHz, however, the TL can be influenced considerably well by the actuation pressure applied, due to a damping-dominated behaviour around the critical frequency. Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

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12 pages, 2558 KiB

Open AccessArticle

An Investigation on the Sound Absorption Performance of Granular Molecular Sieves under Room Temperature and Pressure

by Bing Zhou, Jiangong Zhang, Xin Li and Bilong Liu

Materials 2020, 13(8), 1936; https://doi.org/10.3390/ma13081936 - 20 Apr 2020

Cited by 7 | Viewed by 2384

Abstract

The sound absorption of granular silica-aluminate molecular sieve pellets was investigated in this paper. The absorption coefficients of molecular sieve pellets with different pore sizes, pellet sizes, and layer thicknesses were measured through impedance tubes under room temperature and pressure conditions. The effects of pore size, pellet size, layer thickness were compared and explained. The comparisons show that at room temperature and pressure, the sound absorption of molecular sieve pellets is not a result of the crystalline structure, but rather it mainly changes with the pellet size and layer thickness. In addition, the five non-acoustical parameters of molecular sieve pellets were obtained by an inverse characterization method based on impedance tube measurements. The measurement by impedance tubes is in good agreement with the calculation of Johnson-Champoux-Allard (JCA) model, proving that the JCA model can be effectively used to predict the sound absorption of molecular sieve pellets. Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

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13 pages, 5817 KiB

Open AccessArticle

Characterization and Vibro-Acoustic Modeling of Wood Composite Panels

by Andrea Santoni, Paolo Bonfiglio, Patrizio Fausti, Cristina Marescotti, Valentina Mazzanti and Francesco Pompoli

Materials 2020, 13(8), 1897; https://doi.org/10.3390/ma13081897 - 17 Apr 2020

Cited by 6 | Viewed by 2528

Abstract

Natural fiber-filled polymers offer good mechanical properties and economic competitiveness compared to traditional materials. Wood flour is one of the most widely used fillers, and the resulting material, known as wood plastic composite (WPC), has already found a wide applicability in many industrial sectors including automotive and building construction. This paper, as a followup of a previous study on a numerical-based approach to optimize the sound transmission loss of WPC panels, presents an extensive numerical and experimental vibro-acoustic analysis of an orthotropic panel made out of WPC boards. Both structural and acoustical excitations were considered. The panel radiation efficiency and its transmission loss were modeled using analytic and semi-analytic approaches. The mechanical properties of the structure, required as input data in the prediction models, were numerically determined in terms of wavenumbers by means of finite element simulations, and experimentally verified. The accuracy of the predicted acoustic performances was assessed by comparing the numerical results with the measured data. The comparisons highlighted a significant influence of the junctions between the WPC boards, especially on the panel’s transmission loss. The radiation efficiency results were mostly influenced by the boundary conditions of the plate-like structure. This latter aspect was further investigated through a finite element analysis. Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

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12 pages, 3581 KiB

Open AccessArticle

Diffuse Sound Absorptive Properties of Parallel-Arranged Perforated Plates with Extended Tubes and Porous Materials

by Dengke Li, Daoqing Chang and Bilong Liu

Materials 2020, 13(5), 1091; https://doi.org/10.3390/ma13051091 - 01 Mar 2020

Cited by 13 | Viewed by 2214

Abstract

The diffuse sound absorption was investigated theoretically and experimentally for a periodically arranged sound absorber composed of perforated plates with extended tubes (PPETs) and porous materials. The calculation formulae related to the boundary condition are derived for the periodic absorbers, and then the equations are solved numerically. The influences of the incidence and azimuthal angle, and the period of absorber arrangement are investigated on the sound absorption. The sound-absorption coefficients are tested in a standard reverberation room for a periodic absorber composed of units of three parallel-arranged PPETs and porous material. The measured 1/3-octave band sound-absorption coefficients agree well with the theoretical prediction. Both theoretical and measured results suggest that the periodic PPET absorbers have good sound-absorption performance in the low- to mid-frequency range in diffuse field. Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

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11 pages, 3037 KiB

Open AccessArticle

The Influence of Environmentally Friendly Flame Retardants on the Thermal Stability of Phase Change Polyurethane Foams

by Dong Liu and Anjie Hu

Materials 2020, 13(3), 520; https://doi.org/10.3390/ma13030520 - 22 Jan 2020

Cited by 15 | Viewed by 2343

Abstract

To improve thermal insulation, microencapsulated phase change materials (micro-PCMs), expandable graphite (EG), and ammonium polyphosphate (APP) were introduced into polyurethane foam (PUF) to enhance the thermal stability and improve the thermal insulation behavior. The morphology of the PUF and micro-PCM was studied using a scanning electronic microscope (SEM), while the thermophysical properties of the PUF were investigated using a hot disk thermal constants analyzer and differential scanning calorimetry (DSC). The thermal stability of the PUF was investigated by thermogravimetric analysis (TGA), and the gas products volatilized from the PUF were analyzed by thermogravimetric analysis coupled with Fourier transform infrared spectrometry (TGA-FTIR). The results revealed that the thermal conductivities of the PUF were reduced because micro-PCM is effective in absorbing energy, showing that the PUF functions not only as a thermal insulation material but also as a heat sink for energy absorption. Moreover, the EG and APP were found to be effective in improving the thermal stabilities of the PUF, and the optimized formulation among EG, APP, and micro-PCMs in the PUF showed a significant synergistic effect. Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

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18 pages, 6553 KiB

Open AccessArticle

Composite Eco-Friendly Sound Absorbing Materials Made of Recycled Textile Waste and Biopolymers

by Chiara Rubino, Marilés Bonet Aracil, Jaime Gisbert-Payá, Stefania Liuzzi, Pietro Stefanizzi, Manuel Zamorano Cantó and Francesco Martellotta

Materials 2019, 12(23), 4020; https://doi.org/10.3390/ma12234020 - 03 Dec 2019

Cited by 44 | Viewed by 6040

Abstract

In recent years, the interest in reusing recycled fibers as building materials has been growing as a consequence of their ability to reduce the production of waste and the use of virgin resources, taking advantage of the potential that fibrous materials may offer to improve thermal and acoustic comfort. Composite panels, made of 100% wool waste fibers and bound by means of either a chitosan solution and a gum Arabic solution, were tested and characterized in terms of acoustic and non-acoustic properties. Samples with a 5 cm thickness and different density values were made to investigate the influence of flow resistivity on the final performance. Experimental results demonstrated that the samples had thermal conductivity ranging between 0.049 and 0.060 W/(m K), well comparable to conventional building materials. Similarly, acoustic results were very promising, showing absorption coefficients that, for the given thickness, were generally higher than 0.5 from 500 Hz on, and higher than 0.9 from 1 kHz on. Finally, the effects of the non-acoustic properties and of the air gap behind the samples on the acoustic behavior were also analyzed, proving that the agreement with absorption values predicted by empirical models was also very good. Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

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15 pages, 4804 KiB

Open AccessArticle

Variability and Performance Study of the Sound Absorption of Used Cigarette Butts

by Valentín Gómez Escobar, Guillermo Rey Gozalo and Carlos J. Pérez

Materials 2019, 12(16), 2584; https://doi.org/10.3390/ma12162584 - 14 Aug 2019

Cited by 13 | Viewed by 2654

Abstract

There has been increasing interest in new sustainable materials that can be used as construction materials. Among them, sound-absorbing materials have an important role in both acoustical room conditioning and in room insulation. As a proposal for recycling, one of the most common residues in the world, cigarette butts, is studied. Samples were prepared with used cigarette butts as acoustical absorbent materials. Several samples were prepared and grouped by similarity. Variability analyses of the samples prepared in each group were performed. Moreover, the analysis of some possible influences on absorption properties, such as the length of butts, presence of burnt regions, presence of wrapping paper, etc., were analyzed. The results show the potentiality of this residue to be used as an acoustical absorbent since the absorption coefficients found are greater than 0.8 for frequencies over 2000 Hz. The observed variability in the study group and samples can be considered low, as it was below 2% for the major part of frequencies. Influences on the absorption coefficient, for both the length and status of the butts, were statistically confirmed. Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

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11 pages, 1447 KiB

Open AccessArticle

Design of Multiple Parallel-Arranged Perforated Panel Absorbers for Low Frequency Sound Absorption

by Xin Li, Qianqian Wu, Ludi Kang and Bilong Liu

Materials 2019, 12(13), 2099; https://doi.org/10.3390/ma12132099 - 29 Jun 2019

Cited by 32 | Viewed by 3725

Abstract

A particular structure that consists of four parallel-arranged perforated panel absorbers (PPAs) is proposed for the low frequency sound absorption within a constraint space. The apertures of the perforated panels are set to ≥1.5 mm, and the number of orifices is much less and therefore easier to be produced in comparison with that of the micro perforated panel (MPP). A simple approximation model by using acoustic-electrical analogy is described to calculate the sound absorption coefficient of such device subject to normal wave incidence. Theoretical and experimental results demonstrate that the device can provide more than one octave sound absorption bandwidth at low frequencies. Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

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Review

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28 pages, 3823 KiB

Open AccessReview

Acoustic Properties of Innovative Concretes: A Review

by Roman Fediuk, Mugahed Amran, Nikolai Vatin, Yuriy Vasilev, Valery Lesovik and Togay Ozbakkaloglu

Materials 2021, 14(2), 398; https://doi.org/10.3390/ma14020398 - 14 Jan 2021

Cited by 68 | Viewed by 7979

Abstract

Concrete is the most common building material; therefore, when designing structures, it is obligatory to consider all structural parameters and design characteristics such as acoustic properties. In particular, this is to ensure comfortable living conditions for people in residential premises, including acoustic comfort. Different types of concrete behave differently as a sound conductor; especially dense mixtures are superior sound reflectors, and light ones are sound absorbers. It is found that the level of sound reflection in modified concrete is highly dependent on the type of aggregates, size and distribution of pores, and changes in concrete mix design constituents. The sound absorption of acoustic insulation concrete (AIC) can be improved by forming open pores in concrete matrices by either using a porous aggregate or foam agent. To this end, this article reviews the noise and sound transmission in buildings, types of acoustic insulating materials, and the AIC properties. This literature study also provides a critical review on the type of concretes, the acoustic insulation of buildings and their components, the assessment of sound insulation of structures, as well as synopsizes the research development trends to generate comprehensive insights into the potential applications of AIC as applicable material to mitigate noise pollution for increase productivity, health, and well-being. Full article

(This article belongs to the Special Issue Innovative Composite Materials for Sound Absorption and Insulation)

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