Search Results (203)

Addressing the challenges of bulky, low-efficiency sound-insulation materials at low frequencies, this work proposes an acoustic metamaterial based on curve fractal channels. Each unit cell comprises a concentric circular-ring channel recursively iterated: as the fractal order increases, the channel path length grows exponentially, enabling outstanding sound-insulation performance within a deep-subwavelength thickness. Finite-element and transfer-matrix analyses show that increasing the fractal order from one to three raises the number of bandgaps from three to five and expands total stop-band coverage from 17% to over 40% within a deep-subwavelength thickness. Four-microphone impedance-tube measurements on the third-order sample validate a peak transmission loss of 75 dB at 495 Hz, in excellent agreement with simulations. Compared to conventional zigzag and Hilbert-maze designs, this curve fractal architecture delivers enhanced low-frequency broadband insulation, structural lightweighting, and ease of fabrication, making it a promising solution for noise control in machine rooms, ducting systems, and traffic environments. The method proposed in this paper can be applied to noise reduction of transmission parts for ceramic automation production. Full article

To meet the European Green Deal targets, the construction sector must improve building thermal performance via advanced insulation systems. Eco-friendly sandwich panels offer a promising solution. Therefore, this work aims to develop and validate a new eco-friendly composite sandwich panel (basalt fibres and recycled extruded polystyrene) with enhanced multifunctionality for lightweight and energy-efficient building façades. Two panels were produced via vacuum infusion—a reference panel and a multifunctional panel incorporating phase change materials (PCMs) and silica aerogels (AGs). Their performance was evaluated through lab-based thermal and acoustic tests, numerical simulations, and on-site monitoring in a living laboratory. The test results from all methods were consistent. The PCM-AG panel showed 16% lower periodic thermal transmittance (0.16 W/(m²K) vs. 0.19 W/(m²K)) and a 92% longer time shift (4.26 h vs. 2.22 h), indicating improved thermal inertia. It also achieved a single-number sound insulation rating of 38 dB. These findings confirm the panel’s potential to reduce operational energy demand and support long-term climate goals. Full article

Mycelium-based composites (MBCs) are an emerging category of cost-effective and environmentally sustainable materials that are attracting significant research and commercial interest across various industries, including construction, manufacturing, agriculture, and biomedicine. These materials harness the natural growth of fungi as a low-energy bio-fabrication method, converting abundant agricultural by-products and waste into sustainable alternatives to energy-intensive synthetic construction materials. Their affordability and eco-friendly characteristics make them attractive for both research and commercialisation. Currently, mycelium-based foams and sandwich composites are being actively developed for applications in construction. These materials offer exceptional thermal insulation, excellent acoustic absorption, and superior fire safety compared to conventional building materials like synthetic foams and engineered wood. As a result, MBCs show great potential for applications in thermal and acoustic insulation. However, their foam-like mechanical properties, high water absorption, and limited documentation of material properties restrict their use to non- or semi-structural roles, such as insulation, panelling, and furniture. This paper presents a comprehensive review of the fabrication process and the factors affecting the production and performance properties of MBCs. It addresses key elements such as fungal species selection, substrate choice, optimal growth conditions, dehydration methods, post-processing techniques, mechanical and physical properties, termite resistance, cost comparison, and life cycle assessment. Full article

The significant waste generated by construction has increased interest in sustainable solutions, including prefabricated interior partition panels. Although different types of alternative panels have been proposed, their performance as interior partitions remains underexplored in systematic comparative studies. To narrow this knowledge gap, this paper presents a comprehensive evaluation and classification of drywall, OSB (Oriented Strand Board), cement–wood, and honeycomb panels, regarding physical, mechanical, microstructural, thermal, acoustic, and combustibility characteristics, in addition to conducting a cost evaluation. The results indicated that the OSB panels exhibited superior results for interior partition applications, showing notable advantages in physical strength, mechanical performance, and thermal insulation, while offering acoustic properties comparable to those of drywall panels. Nevertheless, OSB panels showed lower fire resistance and were associated with the highest cost among the materials analyzed in the present research. Drywall panels, on the other hand, provided the most favorable fire resistance but exhibited the least effective thermal insulation. The findings also indicated that both wood–cement and honeycomb panels require further improvements in their manufacturing processes to meet performance standards suitable for interior partition. Full article

This article provides a comprehensive analysis of the acoustic properties of recycled rubber crumb, examined in two forms—loose granular and compacted specimens. The aim was to compare their acoustic properties depending on the size of the fraction, the thickness of the sample, and the degree of compaction, with measurements performed using a model BSWA SW433 impedance tube in the frequency band 100–2500 Hz. Experimental samples of recycled rubber crumb were prepared with various thicknesses (2, 4.5, and 7 cm) and of various fractions (0–4 mm), and the granular samples were compacted under a pressure of 250–750 kPa. The results showed that the highest transmission loss (TL) is achieved by fine fractions at higher pressure and with greater sample thickness; Fraction 1 (below 1 mm) at a pressure of 750 kPa and a thickness of 7 cm had the best acoustic properties. Through regression analysis, mathematical models of the dependence of transmission loss on the monitored parameters for all types of samples (granular/compacted) were created. The regression analysis confirmed that the thickness, pressure, and size of the fraction significantly affect the acoustic properties of the material. Recycled rubber crumb therefore represents an efficient and environmentally sustainable alternative to traditional insulation materials, and optimizing its parameters enables a wide range of practical acoustic applications in construction, transport infrastructure, and manufacturing industries. Full article

Concerning building acoustics, the impact of sound propagation in the building structure can be considered one of the most relevant problems. Floating floors are an efficient solution, composed of a rigid walking surface above a resilient material. Functioning as a spring, the resilient layer must have adequate damping properties and compressive strength against permanent and imposed loads to guarantee its performance over time. In this context, this study aims to completely evaluate the impact sound reduction of composite lightweight floating floors formed by ceramic tiles and recycled rubber mats when subjected to prolonged loads, from material characterization to their application in a hypothetical scenario. This study was based on the dynamic stiffness (ISO 9052-1) and compressive creep (ISO 16534) of the resilient layer and the physical characterization of the ceramic tiles, predicting the present and future (15 years) impact sound reductions and their application in a hypothetical room, considering direct and indirect transmissions paths (ISO 12354-2). The results showed that the lightweight floating floor compositions lost their damping capability to a degree that can reduce their weighted reduction in the impact sound pressure level by up to 2 dB over prolonged periods (15 years). Howsoever, the compositions had considerable initial impact sound insulation capability and adequate performance maintenance over time. Full article

Lightweight artificial aggregates (LWAs) are widely used in civil construction, but their conventional production depends on pure clays, a finite natural resource that negatively impacts the environment. This study aims to contribute to minimizing this issue by exploring the use of sustainable ternary mixtures of kaolinitic clay (KC), chamotte residues (CHT), and eucalyptus firewood ash (EFA), promoting a more environmentally friendly approach to the manufacture of LWAs. Thus, the aim was to develop and optimize LWAs using different replacements of industrial waste. Furthermore, the Taguchi method is employed to identify the optimal manufacturing parameters, such as waste content, sintering temperature, and heating time. The research involved the production of 32 distinct mixtures with different proportions of KC, CHT, and EFA, processed through grinding and sintering at temperatures ranging from 1075 °C to 1180 °C. The samples were evaluated for density, water absorption, mechanical strength, and expansion index. Statistical analysis was conducted using ANOVA to validate the most significant factors. The results revealed that mixtures with 80% of waste presented an aggregate expansion index of up to 60%, a minimum bulk density of 1.20 g/cm³ (which aligns with requirements for structural applications but exceeds the maximum bulk density for some lightweight aggregates), and crushing strength higher than 5 MPa, satisfying the normative criteria for commercial LWAs. In addition, 63 industrial applications were identified for the developed materials, ranging from structural lightweight concretes to thermal and acoustic insulation with varied microstructures. Therefore, the partial replacement of clay by CHT and EFA waste represents a promising alternative for producing sustainable LWAs, helping to reduce environmental impacts while providing quality materials for various applications in the most diverse industrial sectors. Full article

In response to the growing demand for sustainable and performance-driven building design, this study proposes an integrated digital methodology that combines Building Information Modeling (BIM), parametric scripting, and multi-criteria decision-making (MCDM) to optimize external wall assemblies. The approach leverages Autodesk Revit and Dynamo to automate the parametrization of insulation thickness while ensuring compliance with regulatory thresholds for thermal transmittance and surface mass. Acoustic performance is estimated using ECHO software, and a Weighted Sum Model (WSM) is applied to evaluate and rank configurations based on four criteria: economic cost, Global Warming Potential (GWP), embodied energy, and acoustic insulation. A case study involving 24 wall assemblies—generated from eight base stratigraphies and three insulation materials—demonstrates the method’s ability to balance environmental impact, occupant comfort, and construction feasibility. The results indicate that natural and bio-based materials, such as rammed earth and cork, offer the best overall performance, while conventional systems remain competitive in terms of cost. The proposed workflow reduces design time, increases transparency, and supports informed decision-making during early design stages. This research contributes to the digitalization of sustainability assessment in architecture by promoting integrative, replicable, and regulation-aligned practices for low-impact building envelopes. Full article

This review article presents a comprehensive analysis of recent advancements in sound insulating materials, focusing on the characterization of material types and their properties from 2015 to 2024. It examined the application of various natural and synthetic materials, including fibrous, porous, composite, polymeric, and advanced materials, in architectural and environmental acoustics. A systematic search in the Scopus database identified relevant articles that were classified according to the material types and their inherent properties. The analysis covered key aspects such as thermal, mechanical, chemical, and physical characteristics, and their impact on sound insulation performance. Unlike previous studies that focused on classic materials or single aspects, this review used analytical and database tools to identify recent research trends. This review highlights the development of advanced and sustainable materials for noise reduction that address challenges in both building acoustics and environmental sound pollution. Full article

The key objectives of both European Union and Portuguese policies are energy efficiency and carbon neutrality in the building sector. Timber construction offers unique advantages in achieving these goals, such as increased productivity through faster and more efficient building processes, using renewable resources with lower carbon emissions during production and throughout the lifecycle, and contributions to forest conservation. However, in many countries, timber construction remains underutilised due to concerns about its thermal and acoustic performance, fire safety, and limited availability of raw materials. This study addresses these challenges by evaluating the potential of various insulation materials, including polystyrenes, mineral wools, natural fibres, composites, and acoustic mats, for incorporation into prefabricated timber components. Key performance criteria included thermal insulation, sound absorption, fire reaction, environmental impact, and local availability. Among the materials analysed, glass wool, rock wool, and cork emerged as the most favourable options, offering excellent thermal and acoustic performance and presenting strong results in other key parameters. These findings underscore the potential of incorporating these materials into timber construction systems, contributing to developing sustainable and high-performance building solutions. Full article

High-temperature pipelines, as core facilities in the fields of petrochemical and power, are constantly exposed to extreme working conditions ranging from 450 to 600 °C, facing risks of stress corrosion, creep damage, and other defects. Traditional shutdown inspections are time-consuming and costly. Meanwhile, existing electromagnetic acoustic transducers (EMATs) are restricted by their high-temperature tolerance (≤500 °C) and short-term stability (effective working duration < 5 min). This paper proposes a high-frequency circumferential guided wave (CLamb wave) EMAT based on a Halbach permanent magnet array. Through magnetic circuit optimization (Halbach array) and multi-layer insulation design, it enables continuous and stable detection on the surface of 600 °C pipelines for 10 min. The simulations revealed that the Halbach array increased the magnetic flux density by 1.4 times and the total displacement amplitude by 2 times at a magnet’s large lift-off (9 mm). The experimental results show that the internal temperature of the sensor remained stable below 167 °C at 600 °C. It was capable of detecting the smallest defect of a φ3 mm half-hole (depth half of the wall thickness), with a signal attenuation rate of only 0.32%/min. The signal amplitude of Q235 pipelines under high-temperature short-term detection (<5 min) was 1.5 times higher than that at room temperature. However, material degradation under high temperature led to insufficient long-term stability. This study breaks through the bottleneck of long-term detection of high-temperature EMATs, providing a new scheme for efficient online detection of high-temperature pipelines. Full article

Urbanization and population growth have heightened the need for sustainable, efficient building materials that combine acoustic and thermal insulation with environmental and economic sustainability. Sandwich composite panels have gained attention as versatile solutions, offering lightweight structures, high strength, and adaptability in construction applications. This study evaluates manual, semi-automatic, and automatic production methods, selecting the automatic process for its efficiency, precision, and suitability for large-scale production. Extensive characterization techniques, including field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), Differential Thermogravimetry (DTG), Differential Scanning Calorimetry (DSC), and flammability tests, were employed to evaluate the morphological, thermal, acoustic, and fire-resistant properties of the panels. The P200 sample, produced automatically, demonstrated high acoustic absorption in the mid–high frequencies (2000–4000 Hz), strong interlayer adhesion, and low thermal conductivity (2.75 W/mK), making it effective for insulation applications. The flammability tests confirmed compliance with EPA 1030 standards, with a low flame propagation rate (1.55 mm/s). The TGA-DTG and DSC analyses revealed the thermal stability of the panel’s components, with distinct degradation stages being observed for the polyurethane core and non-woven textile layers. The FE-SEM analysis revealed a compact and homogeneous structure with strong adhesion between the core and textile layers. These results highlight the potential of sandwich composites as eco-friendly, high-performance materials for modern construction. Full article

The lightweight development trend of modern residential structures reduces sound attenuation in buildings and makes sound propagation paths more complex. Neighbor-induced impact sound has become a significant source of residents’ dissatisfaction with the acoustic environment. To gain a deeper understanding of the characteristics of residential impact sound, reduce its impact on users, and improve the quality of residential buildings, a systematic review of existing research based on PRISMA2020 was carried out. Articles indexed in the Web of Science core dataset and Scopus were searched, with a cutoff date of October 2024. After screening and reviewing, 132 articles were systematically analyzed, categorizing the research on floor impact sound into four aspects, namely impact sound sources, evaluation indicators, prediction methods, and improvement measures. The results show that due to the diversity of real sound sources and differences in living habits, the standard impact sound sources in different countries or regions still need further study. Both subjective and objective evaluations indicate that heavyweight impact sound, particularly low-frequency sound, has the greatest impact on occupants and is the most difficult to eliminate. The physical characteristics of floor impact sound can be predicted using methods such as finite element analysis. However, there are fewer prediction methods for subjective evaluations due to the poor correlation between subjective and objective evaluation indicators. Though different soundproofing measures significantly improve the sound insulation of impact sound, they are still not widely applied due to materials, construction techniques, and time and economic costs. This study provides a reference for research on residential impact sound in China and offers an outlook for future research directions. Full article

Given the current need to improve the thermal and energy performance of buildings, special attention has been given to the building envelope and materials. Concrete sandwich panels (CSPs) are versatile composite construction elements whose popularity is increasing given their properties, e.g., good thermal and acoustic insulation, durability, and fire resistance. Nevertheless, besides their properties, it is important to evaluate the sustainability of composite panels under development. This work aims to assess the eco-efficiency of six CSPs with distinct insulation materials: lightweight concrete (LWC), cork, glass wool, and expanded polystyrene (EPS). Coupling both life cycle assessment (LCA) and life cycle costing (LCC) analysis, this study derives eco-efficiency indicators to inform decisions regarding CSP environmental and economic performances. The results of the LCA and LCC showed that the high-performance concrete (HPC) layer was the main hotspot of the CSPs in all scenarios. Moreover, the best scenario changed when different environmental impact categories were considered. Thus, using multiple environmental indicators is recommended to avoid problem-shifting. Considering the final cost, the CSP with cork is the most expensive panel to produce, with the other five options having very similar manufacturing prices. On average, raw material inputs, labour, and material delivery account for 62.9%, 18.1%, and 17.1% of the total costs, respectively. Regarding the eco-efficiency results, the most eco-efficient scenario changed with the environmental indicator used. Cork seems to be the best option when considering the carbon footprint of the panels, whereas when considering other environmental indicators, the recycled EPS scenario has the best eco-efficiency and the CSP with cork the worst. Full article

Considering the growing need for developing ecological materials, this study investigates the acoustic, mechanical, and thermal properties of wood composites reinforced with beech or oak wood fibres. Scanning electron microscopy (SEM) revealed a complex network of interconnected pores within the composite materials, with varying pore sizes contributing to the material’s overall properties. Acoustic characterization was conducted using a two-microphone impedance tube. The results revealed that the fibre size significantly impacts the sound absorption coefficient, demonstrating that the highest sound absorption coefficient of 0.96 corresponds to the composites reinforced with oak wood fibres with a size of 2 mm in the low-frequency range of 1000–2500 Hz. Mechanical testing revealed a significant reduction in compressive strength as fibre size increased from 0.4 mm to 2 mm, correlating with the observed changes in sound absorption and thermal properties. Thermal analysis indicated thermal conductivity (λ) values ranging from 0.14 to 0.2 W/m·K, with a notable increase in conductivity as fibre size decreased. It was shown that composites reinforced with beech or oak wood fibres with a size of 2 mm are recommendable for insulation materials due to the lowest thermal conductivity of 0.14 W/(m·K). Oak wood composites with a fibre size of 0.4 mm recorded the highest heat capacity, which is 54.4% higher than the one corresponding to the composites reinforced with the largest fibres. The results regarding heat diffusion rates are also reported. The findings about the effects of fibre size and pores on thermal, acoustic and mechanical properties provide valuable insights for designing sustainable materials, offering potential applications in industries where balanced performance across multiple properties is required. Full article