Acoustic Insulation Research Articles

Experimental study of the effect of the addition of Posidonia Oceanica fiber on the thermal and acoustic insulation properties of plaster

In this work, plaster and natural Posidonia Oceanica (PO) fibers are combined to create a composite material that was recently produced. This work’s primary objective is to assess the mechanical and thermophysical performance of the composite material in order to determine whether or not it may be used as a thermal and acoustic insulation material in buildings. For this end, prismatic and parallelepipedic specimens of different dimensions were made with fiber percentages ranging from 0% to 20%. In addition, parallelepiped panels (600 mm × 600 mm × 40 mm3) were also prepared containing 10% of PO fibers. Mechanical properties (flexual strength, compressive strength), thermal properties and sound absorption coefficient were investigated. For each test specimen, the density was calculated for a proportion of fibers ranging from 0% to 20%. The results indicated a marked improvement in the compressive and flexural strength of the fiber-reinforced mixtures. This improvement is respectively 14.5% and 33.8% for mixtures containing 10% of PO fibers. Additionally, the addition of PO fibers significantly decreases density (by 40.5%), thermal conductivity (by 68.5%) and thermal diffusivity (by 36.9%) of the different mixtures. The ideal mechanical characteristics are attained when 5%–10% of the volume is made up of Posidonia Oceanica fibers. The results of the sound absorption coefficient test show that the mixture of plaster with 10% fibers has a good sound absorption coefficient of 0.78 for high frequencies between 1000 Hz and 4000 Hz. This work has shown conclusively that the incorporation of PO fibers, up to a maximum of 10% with plaster, makes it possible to obtain a lightweight composite that can potentially be used as a new insulating construction material.

Vibro-acoustic topology optimization for improving the acoustic insulation and mechanical stiffness performance of periodic sandwich structure

The traditional parameter adjustment design makes it difficult to effectively regulate the acoustic insulation performance of periodic sandwich structures while meeting the lightweight and mechanical stiffness requirements. A dynamic three-field floating projection topology optimization (FPTO) method for periodic structures is proposed to meet the optimization requirements of low-noise and high-stiffness performance of lightweight periodic sandwich structures. The sound transmission loss is taken as the optimization objective, and the lightweight volume and mechanical stiffness performance are taken as the multiple constraints. The results show that a smooth topology configuration with superior sound insulation performance, high stiffness, and a freely customizable number of periodic cores can be obtained via the proposed method. The accuracy and effectiveness of the presented method are verified via 3D printing technology and impedance tube sound insulation experiments, providing an important reference for the optimal design of lightweight composite structures for vibration and noise reduction in transportation equipment.

Performance Study on Laterite Block with Perlite

Abstract The term “perlite” refers to an amorphous volcanic silicate/alumina rock that can expand at temperatures between 900 and 1200 ∼C when heated fast. Because perlite is so versatile, it can be applied in a variety of sectors, including construction, horticulture, petrochemical, and industrial. An item that is used in the construction sector is expanded perlite (EP). It can be used as an input for geopolymers or mixed with aggregate or cement to create conventional cementitious materials. EP offers low density, effective thermal and acoustic insulation, and exceptional fire resistance for buildings. Perlite appears to be a necessary material as a result. The author of this article examines the effects of EP, a chemical used in building materials, on the properties of geopolymers, different types of binder, and regular cementitious materials, both in their fresh and hardened states. The usefulness of using perlite-reinforced laterite blocks as a sustainable building material is investigated in this work. We investigate this composite’s potential for usage in building applications by thoroughly examining its mechanical and thermal properties. The results provide insight into how robust and eco-friendly construction practices could be supported by increasing structural strength and thermal efficiency.

Polymeric Wastes as Concrete Aggregate for Acoustic and Thermal Insulation Enhancement

Polymeric Wastes as Concrete Aggregate for Acoustic and Thermal Insulation Enhancement

The Role of Building-Integrated Greenery Systems in Building Sustainability Rating Systems

Building rating systems allow for the evaluation of environmental buildings’ impact throughout their lifecycle, thereby enabling improved design. The integration of vegetation into building envelopes, through green roofs and facades, provides multiple benefits that enhance the sustainability of a built environment. In arid climates, Building-Integrated Greenery Systems (BIGSs) contribute to energy savings and the improvement of the urban environment through evaporative cooling. However, the maintenance of these green systems requires efficient water use. This study thoroughly reviews six selected building sustainability certifications to determine the extent to which BIGSs are considered in the certification process. The findings indicate that BIGSs are not yet well integrated directly into these certifications. While the certifications recognize the biophilic effects on users and contributions to sustainable construction, they often overlook scientifically proven benefits such as acoustic insulation and urban noise reduction. This study highlights the importance of updating certification frameworks to fully incorporate the diverse advantages of BIGSs, especially in enhancing indoor environments and achieving energy savings.

Underwater Acoustic Camouflage by Wettability Transition on Laser Textured Superhydrophobic Metasurfaces

AbstractThe superhydrophobicity of submerged surfaces typically pertains to the trapped air film at the liquid–solid interface, subject to wettability transitions from a Cassie–Baxter state to more unstable states that gradually collapse to high retention regimes, which are energetically more favorable. In this work, the dynamic evolution of those transient metastable states is correlated to the underwater acoustic performance of laser textured superhydrophobic surfaces, resolving the dependence of the ultrasound spectral response with the immersion time to capture the genuine contribution of the hierarchical subwavelength morphology, regardless of the air layer effects. Acoustic wave attenuation of the incident ultrasound energy is extensively quantified in transmission, accounting for instantaneous broadband sound blocking (>30 dB) within the spectral range 0.5–1.5 MHz. As a result of the air layer detachment with the immersion time, transmission coefficients increase accordingly, while acoustic fields in reflection unexpectedly evolve toward stealthiness and naïve acoustic camouflage, mostly ascribable to dissipative mechanisms at air layer interfaces. The intrinsic decay of the air layer effect is tentatively determined at different frequencies, since quantitative understanding of the transient lifetime governing underwater surface wettability is critical to design stable superhydrophobic character of laser induced subwavelength metastructures on the most promising acoustic materials – from eco‐friendly natural to artificial.

Effect of Drying Methods on the Thermal and Mechanical Behavior of Bacterial Cellulose Aerogel.

Bacterial cellulose (BC) presents significant promise as a biomaterial, boasting unique qualities such as exceptional cellulose purity, robust mechanical strength, heightened crystalline structure, and biodegradability. Several studies have highlighted specific effects, such as the impact of dehydration/rehydration on BC tensile strength, the influence of polymer treatment methods on mechanical properties, the correlation between microorganism type, drying method, and Young's modulus value, and the relationship between culture medium composition, pH, and crystallinity. Drying methods are crucial to the structure, performance, and application of BC films. Research findings indicate that the method used for drying can influence the mechanical properties of BC films, including parameters such as tensile strength, Young's modulus, and water absorption capacity, as well as the micromorphology, crystallinity, and thermal characteristics of the material. Their versatility makes them potential biomaterials applicable in various fields, including thermal and acoustic insulation, owing to their distinct thermal and mechanical attributes. This review delves into the thermal and mechanical behavior of bacterial cellulose aerogels, which are profoundly impacted by their drying mechanism.

Application of Cellulose and Paper-Based Products in Building Acoustics

This article presents a comprehensive acoustic study of paper-based building products: cellulose wool, paperboard, corrugated cardboard, and honeycomb panels. The material configurations included the intact form as well as the various modifications, i.e., density variation, multiple-layered staking, perforation or acoustic metamaterial setup. Tests covered acoustic absorption and insulation properties, with the last examined under excitation of both a plane wave and a diffused field. Additionally, the cellulose wool is provided with the characteristic impedance and propagation wavenumber results; and the paperboard was tested for its dynamic elastic and damping properties. The paper-based products, giving their weight, prove to be a convincing replacement for conventional materials by both absorptive and insulation performance. The maximum acquired sound reduction index, for exceptionally lightweight (2.2 kg/m2) paper double-wall metamaterial structure, reached 26 dB.

Evaluation of different acoustic insulation methods in CLT structures

This study explores the efficacy of various structural noise insulation systems implemented in the construction of pilot houses made from Cross-Laminated Timber (CLT). Focusing on both vertical and lateral transmission, the research aims to evaluate the performance of different insulation methods in mitigating structural noise within these innovative wooden structures. The investigation involves a comprehensive testing regimen to assess the impact of insulation systems on noise reduction, considering both practical applications and theoretical considerations. The findings of this study contribute valuable insights into enhancing the acoustic performance of CLT pilot houses, thereby informing best practices for noise insulation in wooden construction systems.

Drying time of plaster within in-fill plasterboard walls and evaporation theory for water within gypsum: methodology, numerical simulation and application

ABSTRACT The desulphurisation-gypsum-filling-wall (DSG-FW) formed by pouring into plasterboard partitions with desulphurisation gypsum slurry can utilise low-quality desulphurisation gypsum and also improve the acoustic insulation issues arising from the use of hollow partitions. The construction schedule of this wall is unable to be controlled because the moisture transfer characteristics in DSG-FW are unclear. Therefore, it is important to determine the drying time and the moisture-transfer behaviour during the construction process. By using different thicknesses of gypsum samples, adding different amounts of perlite and adjusting the relative humidity, whether the gypsum board is covered, the drying and evaporating process of gypsum was compared and analysed. The evaporative characteristics of the desulphurisation gypsum core wall at different relative humidities were determined through experiments. In addition, an evaporation model was introduced for simplification and verification. The experimental results show that the drying of gypsum is correlated with relative humidity and gypsum thickness: the higher the relative humidity, the lower the evaporation rate; the thicker the gypsum, the longer the drying time; perlite and gypsum board have no effect on gypsum drying. The rate of evaporation of DSG-FW increases non-linearly with the decrease in relative humidity under which the DSG-FW is conditioned; the simplified Hertz-Knudsen-Langmuir (HKL-S) model can only be used to predict the evaporation behaviour within the higher relative humidity range (more than 55% RH), while the simplified statistical rate theory (SRT-S) model was verified as being able to predict the rate of evaporation across almost the whole relative humidity range. The SRT-S model can be used to predict and control the construction of DSG-FW in actual engineering work.

Shift from Traditional to Modern Building Concepts and Designs in Ringim Town: A Comparative Study of Aesthetics, Values, Functions and Durability

This study is part of an Undergraduate Project for the award of “B.Tech (Hons) Building Technology Education” at the “Abubakar Tafawa Balewa University”, Bauchi State, Nigeria, and is aimed to identify the contrasts between Traditional and Modern Buildings in Ringim Town, Jigawa State, Northern Nigeria, with respect to their “Purposes, Durability, Aesthetics and Values. The study's subjects were the residents of Ringim Town, with 88 respondents drawn from ten cohorts of young people (under 40) and Adults (over 40) living in the Katutu, Galadanchi, Walawa, Majiyawar-Gari, and Marakawa Quarters. In order to better understand the shift from traditional to modern building concepts and designs in Ringim, the study used a quantitative approach, specifically a structured questionnaire that focused on groups of youths and adults and asked questions about functions, durability, aesthetics, and values. The answers to the research questions were analyzed using the simple mean and standard deviation. The study's conclusions showed that while traditional buildings in Ringim had greater fire, acoustic, and thermal insulation, they also have poor water resistance, to name a few drawbacks. It is advised that experts in the fields of Architecture, Town planning, and Construction, among others, pay attention to the indigenous Design theory, Technology, Artisanship, and Craftsmanship connected to the emergence of Traditional Building. Additionally, recommendations indicated that, for comparative purposes, comparable studies had to be carried out at other tiers of educational establishments, such as Colleges, Polytechnics, and Universities, as well as in other parts of the State and Nation.

Assessing carbon in timber buildings: how to factor in connections, fire protection and soundproofing

The embodied carbon of timber buildings is often miscalculated at early design stages. Primary materials in mass timber developments typically include glulam and cross-laminated timber, the volume of which is estimated and used to quantify upfront carbon emissions. However, to ensure like-for-like comparisons, the impact of metallic connections and, where needed, fire protection (boarding or treatment) and acoustic insulation should also be considered, even at early stages. This is particularly relevant when comparing timber against concrete schemes, which normally do not require additional allowances for connections, fire protection and soundproofing. This study suggests the upfront embodied carbon of a timber superstructure may increase by up to 60% in residential developments and 30% in commercial buildings when considering secondary components critical to the structure. Note that this is an initial study and that more real-world data should be collated to improve the accuracy of these findings, especially for residential buildings.

Acoustic insulation and directional refraction of dual-functional pentamode metasurface

Acoustic insulation and directional refraction of dual-functional pentamode metasurface

Comprehensive characterization of spathe fibres extracted from Cocos nucifera: physical, chemical, mechanical, thermal, and acoustic properties for insulation applications

In this study, a complete characterization of fibres extracted from the spathe of the Cocos nucifera plant and the properties of spathe fibres are compared with coir fibre extracted from the outer husk of coconut. Coconut spathe fibre is available as bio waste in bulk. The spathe fibres were carefully extracted, pre-treated with NaOH, and porous nonwoven fibre mat were prepared. The physical properties of spathe fibres were measured as per ASTM standards, and average length, diameter, and linear density were found to be 222 mm, 330 μm, and 58.85 tex, respectively. Chemical compositions, XRD analysis, single fibre tensile strength and elongation, morphological analysis by scanning electron microscopy (SEM), and thermal characterization by TGA were also carried out. Spathe fibres treated with NaOH resulted in a 5% reduction in crystallinity index and more surface unevenness and pits. Developing acoustic insulation fibre mat from spathe fibre is a first-of-its-kind study. The sound absorption coefficient of the spathe fibre mat obtained from the impedance tube tester brings out a maximum absorption coefficient of 0.950 at 3150 Hz. The results were compared with coir fibre extracted from the outer husk of coconut and concluded that coconut spathe fibre is a suitable alternative for synthetic and other natural fibres.

Sound transmission loss analysis of novel sandwich plate with star-shaped auxetic cellular cores

A star-shaped auxetic cellular metamaterial with a negative Poisson’s ratio (NPR) was employed in this study to model lightweight sandwich panels, and an analysis of its sound transmission characteristics was conducted. Utilizing the first-order shear deformation theory (FSDT) and the Hamiltonian principle, the free vibration equation for the sandwich plate is derived. Subsequently, leveraging the fluid-structure coupling condition and incorporating the Navier method, the sound transmission loss (STL) is analytically described. The efficacy of the proposed method is validated through numerical analysis and an acoustic insulation experiment using an impedance tube. Based on the theoretical modeling, it is calculated that the sound insulation effect of the star-shaped cellular core exceeds that of the traditional reentrant cellular with NPR. A systematic analysis is subsequently conducted to explore the impact of star-shaped cellular structure parameters on the STL of the sandwich panel. It can be obtained that the increase in core layer thickness leads to a reduction in the first-order resonance frequency of the sandwich panel, but concurrently diminishing its sound insulation performance. The change of the connecting rib length exerts a more considerable influence on the structure’s STL compared to the side rib length. While as the cell wall thickness reduces from 2.0 to 1.0 mm, the average STL of the sandwich plate across the analysis band decreases by 8.43%, from 46.3 to 42.7 dB.

Cleaner Production of Cementitious Materials Containing Bioaggregates Based on Mussel Shells: A Review

This text provides a bibliographic review on bioaggregates obtained from mussel shells and similar materials, evaluating the main properties altered with the use of this type of recycled aggregate in cementitious materials. The bibliographic analysis highlights the main problems and challenges of using bioaggregates related to the presence of organic impurities and chlorides and due to the lamellar and flat shape of the grains, which impair adhesion in the transition zone. The advantages of mussel shell bioaggregates include their limestone-based chemical composition, properties that are inert and compatible with the application, and a specific mass close to conventional aggregates. Regarding their use in cementitious materials, in general, there is a reduction in workability and an increase in incorporated air, porosity, and water absorption, resulting in a reduction in compressive strength. However, it is observed that lower replacement levels make it possible to use bioaggregates, especially fine aggregates, in cementitious materials for different applications, such as structural concrete, coating mortar, and sealing systems. The positive points are related to the promotion of thermal insulation and the reduction in density, which allow for various uses for cementitious materials with bioaggregates, such as lightweight concrete, permeable concrete, and thermal and acoustic insulation mortars. It is concluded that the use of bioaggregates in concrete and mortars is viable, but the need for more experimental work to solve the main problems encountered, such as high water absorption and low compressive strength, is highlighted.

Effect of expanded perlite aggregates and temperature on the strength and dynamic elastic properties of cement mortar

The residential market consumes nearly half of the world’s concrete production, and it is anticipated that 68 % of the global population will reside in urban areas by 2050. Researchers have focused their efforts on exploring alternative options to natural aggregates in concrete and mortar. In line with the principles of circular economy, construction and demolition waste has been repurposed for the manufacture of cement-based materials. Volcanic products, which are abundant but underutilized, have been identified as an alternative to recycled aggregates. They offer several advantages over natural river aggregates, including reduced weight, enhanced thermal and acoustic insulation, improved fire resistance and pozzolanic characteristics. While there has been a significant amount of research on the use of expanded perlite as a supplementary cementitious material, studies involving the use of expanded perlite aggregates (EPA) in cement-based construction materials are relatively limited. This paper seeks to address this knowledge gap by investigating the use of EPA in cement-based mortar at both room and elevated temperatures. The study examines the impact of varying replacement percentages (10 %, 20 % and 30 % - by volume) of natural sand with EPA having a maximum grain size of 4 mm, and the exposure temperature of mortar prisms at the age of 28 days. Specifically, temperatures of 100ºC, 150ºC and 200ºC were selected for analysis. The impact of these parameters on the flexural and compressive strength of mortar, as well as its dynamic elastic properties, was experimentally determined. The findings indicate that, at room temperature, higher replacement percentages of natural sand by EPA result in decreased flexural and compressive strengths, by as much as 50 % and 30.71 %, respectively. However, the dynamic moduli values for replacement percentages up to 20 % are similar to those of the reference mix. Conversely, when subjected to temperatures up to 200ºC, significant improvements were observed in the flexural strength values, e.g. over 20 % for temperatures of 150°C and 200°C, with only marginal improvements in compressive strength, 3 % ÷ 20 % for temperatures of 150°C and 200°C, compared to values obtained at room temperature.

Preparation and Characterization of Particleboard Made from Industrial-Type Wood Particles and Discarded Duck Feathers

Global poultry waste production is substantial, with billions of poultry raised annually for meat and egg production, resulting in significant feather waste. Conventional poultry waste disposal methods are restricted due to environmental concerns. Meanwhile, wood-composite panel industries face raw material shortages, emphasizing the need for sustainable, renewable fiber sources. In this study, in the core layer of panels, wood particles were replaced with 5 wt% clean duck feathers without pretreatment to take advantage of feather attributes like hydrophobicity, thermal insulation, and sound damping as an alternative construction material. Three adhesives—urea-formaldehyde (UF), polymeric 4,4′-diphenylmethane diisocyanate (pMDI), and polyvinyl acetate (PVAc)—were examined for resin–feather compatibility. The control panels in this study were identical but wood was not replaced with feathers. The results revealed that wood–feather particleboard with pMDI and PVAc resins meets the requirements of the relevant standard for P2 boards (where applicable) concerning their modulus of rupture (MOR: 11 N·mm−2), modulus of elasticity (MOE: 1600 N·mm−2), internal bond (IB: 0.35 N·mm−2), and screw withdrawal resistance (SWR). However, those produced with UF resin did not meet the standards for IB and MOE. Furthermore, the physical properties showed similar water resistance and thickness swelling to control panels with pMDI. Notably, substituting 5 wt% wood with feathers improved thermal insulation by approximately 10% for UF and pMDI resins. Additionally, particleboard with feathers demonstrated improved sound absorption at high frequencies, ranging from 2500 to 500 Hz, particularly with pMDI resin, approaching Class B classification according to EN ISO 11654:1997. This study identifies the higher compatibility of pMDI over PVAc and UF adhesives for feather-based composite materials in construction applications.

Development of a vibration-damping, sound-insulating, and heat-insulating porous sphere foam system and its application in green buildings

With the development of green buildings, people pay more attention to the quality of the indoor sound environment. The air sound insulation performance of floors and exterior walls plays a key role in today's green buildings. The thermal performance of the enclosure structure's floor and exterior wall heat transfer resistance is an important factor in reducing building carbon emissions in green buildings. The aim of this paper is to study the efficiency of the acoustic and thermal insulation of a foaming system with porous carbon balls and the combination of different structural ways of construction boards and external walls. The acoustic and thermal parameters of different sound insulation and thermal insulation systems designed with porous carbon sphere foam and inserted into the floors and exterior walls are compared to highlight the optimal structure. The theoretical and experimental tests showed that to improve the sound insulation performance of the floor, a sound insulation system needs to be placed on the surface of the floor in contact with the impact object and inlaid in the vertical gap in contact with the floor and the wall. Furthermore, it has been determined that the surface of the foam particle acoustic ball with micropores has good sound absorption performance. Finally, the high-quality building thermal insulation material with low thermal conductivity in any combination with the floor slabs and the external wall structure improves the thermal insulation performance.

Three-dimensional phononic crystals with self-similar structures

Acoustic metamaterials have the advantages of designability, strong pertinency, small size and good effect, and have good application value in solving the problem of sound insulation and noise reduction. Phononic crystals with wide bandgap and multi-bandgap can inhibit elastic wave propagation to some extent. In this study, a three-dimensional phononic crystal model with self-similar properties is designed by using fractal method. First, an initial unit is constructed, then the arm of the initial unit is replaced with the structure itself to form a self-similar structure. The self-similar model can block sound waves in the wide band and multi-band range. By changing the structure shape and size of phononic crystal, the sound wave blocking in different frequency range is also studied. At the same time of continuous optimization of the structure, the variation rules of the model band structure under different parameters are summarized. To find the good parameters of broadband and multi-band sound wave blocking, so as to achieve the effect of vibration isolation and noise reduction. The finite element method is used to simulate the vibration of the model to verify the existence of elastic wave bandgap. Phononic crystals have a good prospect in the field of sound insulation and noise reduction.