Search Results (412)

The valorization of post-consumer waste materials is an important strategy for reducing environmental impact and supporting circular material use. In this study, lightweight sandwich composites were developed using recycled paper and cardboard as core materials, producing sustainable panels for thermal and acoustic insulation. Core panels were manufactured from 100% paper, 100% cardboard, and a 50–50% paper–cardboard mixture. Environmentally friendly foaming agents were added to increase porosity and reduce density. The cores were subsequently combined with 3 mm medium-density fiberboard (MDF), 1 mm oak veneer, and date palm midrib fibers to provide different surface characteristics. The resulting sandwich composites were evaluated through standardized measurements of thermal conductivity and sound absorption coefficients. Microstructural characteristics were investigated using stereomicroscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX). The results indicate that both the core composition and the type of face layer influence their performance. Whilst composites with cardboard-rich cores had higher porosity and better thermal insulation, introducing perforations and increasing the panel thickness improved sound absorption. The findings demonstrate that recycled paper and cardboard can be effectively used as sustainable raw materials to produce lightweight sandwich composites, tested at material scale, for non-structural interior insulation/acoustic panels. Full article

Low-frequency impact sound control remains a critical challenge for floating floor systems. Conventional resilient underlayment materials exhibit insufficient damping and are prone to long-term deformation, making stable low-frequency sound insulation difficult to achieve. This study presents the development of a composite floating floor underlayment comprising recycled rubber granules, polymer resin, and quartz sand. Based on the constrained layer damping-inspired (CLD-inspired) perspective, the vibration attenuation and noise reduction mechanism is elucidated, and the material’s physical properties, mechanical behavior, microstructure, and acoustic performance are systematically investigated. The results indicate that excessively large rubber granules aggravate curing shrinkage cracking. Optimal processing characteristics are achieved with a binder content of 20 wt% and a rubber granule size of 50 mesh. Laboratory characterization reveals that, compared with conventional cross-linked polyethylene (XLPE) foam underlayments, the proposed composite underlayment reduces the impact sound pressure level by an average of 3–5 dB in the low-frequency band below 250 Hz, and the overall sound insulation performance is improved by 10.77%. Dynamic mechanical analysis shows the composite storage modulus declines from 280 MPa at −20 °C to 10 MPa at 80 °C, while the loss factor remains above 0.2 under typical indoor conditions. Such stable viscoelastic behavior enables efficient shear dissipation of low-frequency vibration energy under the CLD-inspired mechanism. Full-scale field testing combined with long-term observation over 3000 loading cycles demonstrates excellent structural compatibility between the underlayment and the gypsum screed, with no cracking or appreciable deformation observed during prolonged service. The weighted impact sound improvement index (ΔLw) attains 15 dB. These findings verify that the CLD-inspired composite underlayment simultaneously achieves efficient low-frequency impact sound control and superior long-term structural stability, providing an innovative material solution and design strategy for impact noise mitigation in residential floating floor applications. Full article

The sound reduction index R is commonly determined using standardized laboratory procedures developed primarily for full-size building elements. However, in many research and development applications, including technical enclosures, lightweight panels, modular components, and new acoustic materials, only reduced-size specimens are available. In such cases, the influence of specimen dimensions and test-opening geometry on the measured sound insulation is not yet fully understood. This study investigates the effect of specimen size and geometry on the measured sound reduction index using a dedicated small-scale coupled reverberation room stand. Measurements were performed for five materials with different mechanical and structural properties: steel, polymethyl methacrylate (PMMA), medium-density fiberboard (MDF), gypsum board, and Sylomer. Six test openings were analyzed, including three square openings, one quasi-square opening, and two rectangular openings. The results show that specimen dimensions can significantly affect the measured values of R, especially in the low-frequency range, where modal behavior, boundary conditions, and the relationship between specimen dimensions and acoustic wavelength are important. The influence of specimen size was material-dependent and was more pronounced for stiff plate-like materials than for the highly compliant Sylomer specimen. Comparisons between square and rectangular openings with similar surface areas suggest that, within the investigated range of materials, specimen geometries, and measurement conditions, specimen surface area had a greater influence on R than specimen shape, although geometry can still contribute to the measured differences. The repeatability analysis confirmed that the measurement stand is sensitive to differences related to material type, specimen dimensions, and installation conditions. The proposed methodology may be particularly useful for comparative studies of novel acoustic materials and prototype building elements when only reduced-size specimens are available during the early stages of material development. The results support the use of small coupled reverberation rooms for comparative testing and preliminary material screening, while also showing that reduced-size sound insulation measurements require careful interpretation and cannot be treated as direct substitutes for full-scale standardized tests. Full article

Insulated concrete sandwich panels (ICSPs) are widely utilized in modern building structures due to their excellent combination of energy efficiency and structural load-bearing capacity. However, compared to their mechanical and thermal properties, the sound insulation characteristics of ICSPs remain insufficiently studied, presenting a scientific deficit. In practical engineering, insufficient consideration of these acoustic properties—particularly the “acoustic bridging” induced by connectors—often leads to unpredictable noise transmission, making it difficult for building envelopes to meet stringent modern acoustic codes. To further investigate their acoustic characteristics, this paper extends existing theories on infinite periodic ICSPs to study the airborne sound insulation performance of finite-sized ICSPs. First, analytical models for ICSPs under simply supported on all edges (SS) and clamped on all edges (CC) boundary conditions are derived, wherein the connectors are equivalently modeled as elastic media and discrete elastic springs, respectively. Subsequently, the accuracy and applicability of the analytical models are verified through finite element (FE) models and an airborne sound insulation experiment. Finally, based on the analytical models, a parametric study is conducted to explore the effects of the stiffness of connectors, boundary conditions, and the thickness of the core layer on the sound insulation performance of the ICSPs. The results indicate that connector stiffness has a non-monotonic influence on the sound insulation performance of ICSPs. As the connector stiffness increases, the R_w first decreases and then increases, and the sound insulation performance gradually stabilizes when the connector stiffness becomes sufficiently high. Boundary conditions have a significant effect on the acoustic response. For the reference ICSPs, changing the boundary condition from SS to CC increases the R_w from 49 dB to 62 dB, corresponding to an increment of 13 dB and an approximately 95.0% reduction in the equivalent sound transmission coefficient. When the total panel thickness is kept constant, reducing the core layer thickness from 80 mm to 40 mm increases the R_w from 49 dB to 55 dB under SS boundary conditions and from 62 dB to 66 dB under CC boundary conditions, corresponding to increments of 6 dB and 4 dB, respectively. These improvements are equivalent to reductions of approximately 74.9% and 60.2% in the sound transmission coefficient, though this must be weighed against the inevitable reduction in thermal insulation capacity. Although the sound insulation performance of ICSPs is inferior to that of solid concrete panels (SCPs) of equivalent thickness, with reasonable parameter optimization, their sound insulation indices can significantly exceed the latest requirements of current building codes. By fully accounting for boundary effects in practical engineering, this study provides an analytical basis for the acoustic performance prediction and engineering-oriented optimization of finite-sized ICSPs. Full article

Low-frequency sound insulation remains a major challenge for conventional passive materials, as improved attenuation is usually achieved at the expense of increased thickness and mass. In this work, a smooth fixed third-order ring-curve fractal-maze acoustic metamaterial is proposed for compact low-frequency sound insulation, and a physics-guided long short-term memory–physics prediction surrogate network (LSTM–PPS-Net) tandem framework is developed for its full-spectrum inverse design. Different from conventional Hilbert-type, right-angled, or sharply folded labyrinthine structures, the proposed topology uses recursively arranged curved channels to extend the effective acoustic propagation path and enhance phase accumulation within a limited space. Based on this mechanism, four physically meaningful parameters, namely slit width d, characteristic radius R₃, wall thickness t_w, and inter-column spacing l_E, are selected to construct a low-dimensional design space. A COMSOL–MATLAB automated finite-element method (FEM) workflow is established to generate 1000 valid transmission-loss (TL) spectra over 100–1700 Hz with a 5 Hz interval. For forward prediction, PPS-Net is developed by integrating geometry encoding, frequency-conditioned spectral decoding, and peak-weighted learning. The proposed PPS-Net achieves the best prediction accuracy among the tested models, with a mean absolute error (MAE) of 0.75 dB, a root mean square error (RMSE) of 1.88 dB, and a coefficient of determination (R²) of 0.96, outperforming multi-layer perceptron (MLP), convolutional neural network (CNN) and Transformer models under the same dataset and training protocol. For inverse design, the LSTM encoder extracts frequency-ordered spectral features from the target TL curve, while the frozen PPS-Net decoder provides differentiable acoustic-response feedback, thereby addressing the non-unique mapping from acoustic response to structural parameters. Furthermore, a compactness-oriented optimization strategy is introduced to balance spectral consistency, peak alignment, bandwidth preservation, and occupied-area reduction. In two representative cases, the optimized designs reduce the occupied area by approximately 21% in both representative cases, while maintaining the target attenuation characteristics after FEM verification. These results demonstrate that the proposed framework provides an efficient and physically interpretable route for the full-spectrum inverse design and compact optimization of low-frequency acoustic metamaterials. Full article

Aiming at the technical bottleneck that traditional porous structures can hardly achieve mechanical load-bearing and acoustic regulation simultaneously, this study designs and fabricates three implicit surface porous structures (Gyroid, Diamond, Lidinoid) based on the bionic principle of trabecular bone. Experimental characterization and numerical analysis of their mechano-acoustic coupling performance are systematically carried out. Selective Laser Melting (SLM) technology is employed to realize the integrated forming of 316L bionic structures. Quasi-static compression experiments and finite element simulations are conducted to reveal the progressive deformation mechanism and energy absorption characteristics of different topological configurations. The results indicate that the Diamond structure exhibits the optimal comprehensive performance in terms of load-bearing capacity, specific energy absorption and isotropy. On this basis, the sound absorption and sound insulation performances of the structures are evaluated via an acoustic impedance tube test. The results show that the Diamond structure possesses a remarkably higher sound absorption coefficient and sound insulation value in the high-frequency range than other configurations, demonstrating excellent acoustic energy dissipation and sound wave isolation capability. The research indicates that the synergistic optimization of mechanical and acoustic performances can be achieved by regulating the Triply Periodic Minimal Surface (TPMS) topological configuration. Benefiting from its efficient stress transfer paths and intricate sound wave propagation channels, the Diamond structure realizes the coupling of high load-bearing capacity, superior energy absorption and favorable acoustic performance. This work provides a theoretical basis and technical support for the design of bionic porous structures in multifunctional scenarios such as bone implants and protective noise reduction. Full article

New partially bio-based, waste-derived composites are manufactured from date palm surface fibers (DPSF), waste coffee filters (CFP), and disposable medical isolation gowns (MIG). These three disposable raw materials fill landfills and create an environmental problem. Therefore, the objective of this current study is to use such materials in creating promised thermal insulation and sound absorption boards. Six hybrid composites with different compositions were made using Polyvinyl acetate (PVA) wood adhesive as a binder. Three of them were made of DPSF and MIG, and the other three were composed of DPSF and the CFP. Different tests were performed on the developed composites, such as thermal conductivity measurements, sound absorption and noise reduction determination, surface morphology image analysis, thermogravimetric analysis, and three-point bending tests. The results showed that the thermal conductivity coefficients for the hybrids DPSF + MIG and DPSF + CFP are in the ranges 0.0493–0.0613 W/(m·K) and 0.052–0.065 W/(m·K), respectively, over the temperature range 24–82 °C. The sound absorption coefficient (SAC) is greater than 0.4 for all composites at frequency bands greater than 500 Hz. The noise reduction coefficient (NRC) is ≥0.45 for all composites. Surface morphology images of the composites were also reported. The results also show that the composites are thermally stable at temperatures up to 258.3 °C. The flexural modulus ranges between 5.0 and 8.46 MPa for the medical isolation gown composites and 2.49 and 5.57 MPa for the coffee filter paper composites. The hybrid composites have a lower moisture content of 0.51% to 2.5%. These promising results support the use of these composites for thermal insulation and sound absorption in building construction as alternatives to conventional thermal insulations derived from crude fuels. Full article

As the operational service lifespan of subway rail vehicles increased, the sound insulation of the carbody inevitably deteriorated, leading to heightened noise levels inside the vehicles and significantly compromising passenger comfort. Therefore, the impact of the subway carbody’s sound insulation performance on interior noise throughout its service life was studied. The research of this paper was carried out by combining experimental and simulation methods. Through experimental testing, it examined the sound insulation levels of different vehicle components, including the door, side wall and underframe. The carbody sound insulation with different operational lifetimes was obtained. Subsequently, an acoustic simulation model for interior noise in subway vehicles was established via the statistical energy method, and measured data was used to ensure reliability. Finally, based on the simulation model, the interior noise values under different operational service lifespans were obtained. The influence patterns of varying sound insulation performance across different carbody components on interior noise levels were analyzed. The influence of the change in sound insulation over the operational lifespan on the interior noise was obtained. The findings of this paper hold practical engineering significance for developing noise control strategies and maintenance plans for subway rail vehicles. Full article

This study presents a comprehensive experimental investigation of lightweight cementitious composites incorporating pumice and expanded perlite as sustainable substitutes for conventional aggregate systems. Four replacement ratios (25%, 50%, 75%, and 100%) were evaluated to determine their effects on density, compressive strength, flexural strength, modulus of elasticity, and acoustic insulation properties, including the noise reduction coefficient (NRC) and frequency-dependent sound transmission loss (STL). The results showed that increasing the lightweight aggregate content generally reduced the strength-related mechanical properties while improving acoustic performance, particularly in the mid- and high-frequency ranges. Among all mixtures, the expanded perlite-based PRC-1.0 specimen exhibited the best overall acoustic performance, achieving the highest NRC value and the widest STL range. These findings demonstrate a clear trade-off between mechanical strength and acoustic efficiency, indicating that expanded perlite-based lightweight cementitious composites are promising materials for building applications requiring enhanced sound insulation performance. Full article

To balance load-bearing capacity and acoustic insulation, this study proposes a sandwich reinforced concrete (RC) slab with W-shaped interlayer inclined rebar connectors and investigates their influence on acoustic bridging. A three-dimensional vibro-acoustic finite element modeling approach was adapted to analyze airborne sound insulation and impact sound pressure levels in the frequency domain and was validated against experimental results. Parametric analyses were then conducted to evaluate the effects of connector number, connector geometry, anchorage-end treatment, and core-layer parameters. The results revealed distinct frequency-dependent behavior. The introduction of connectors produced a stable dip in airborne sound insulation near 400 Hz and a pronounced impact-sound peak within 200–400 Hz, both associated with connector-controlled coupled characteristic frequencies. Increasing the number of connectors strengthened interlayer stiffness coupling and intensified acoustic bridging in these frequency ranges. By contrast, optimizing the connector structure or introducing a compliant end layer reduced coupling and improved acoustic insulation. Overall, acoustic performance can be improved by reducing the equivalent coupling stiffness of the connectors, enhancing energy dissipation at the connector ends, and appropriately selecting the core-layer parameters. These measures help suppress the characteristic-frequency response and improve mid- to high-frequency sound insulation. Full article

Traffic noise adversely affects residents near expressways, calling for sustainable noise mitigation solutions. This study developed three eco-friendly sound-absorbing panels from sand, industrial slag, and microporous ceramics. By optimizing aggregate gradation, the influence of porosity and flow resistivity on absorption coefficients was analyzed to determine optimal mix ratios. The panels were integrated into perforated metal noise barriers and evaluated through reverberation room and sound insulation tests. Field simulations using SoundPLAN for a residential project in Taizhou validated real-world performance. Results showed that slag panels achieved a Noise Reduction Coefficient (NRC) of 0.70, while sand and ceramic panels both reached 0.55. All configurations maintained a weighted sound reduction index (R_w) of 25–26 dB. Empirical simulations confirmed that a 2.5 m high barrier keeps noise levels within the 60 dB limit. Compared with traditional glass wool, these inorganic panels offer comparable noise reduction, superior non-combustibility, and better weather resistance, making them effective for frequency-specific noise control in urban engineering applications. Full article

This paper presents a method for determining the reduction in noise transmission provided by small samples of acoustic metamaterials, based on comparative sound intensity measurements. The proposed approach offers an alternative to conventional laboratory methods that require large specimens and controlled acoustic conditions, which limit the rapid testing of prototypes. As part of this study, a mobile and modular measurement setup was developed in the form of a cubic enclosure with replaceable panels, enabling experiments to be conducted under near-real conditions. The measurement methodology is based on determining the difference in sound intensity level, $\Delta L_I$, between a reference configuration and a configuration with an installed metamaterial lining, which allows for the direct evaluation of the increase in sound insulation of the tested partition. To verify the method, a locally resonant metamaterial structure was designed and numerically tuned to a frequency of approximately 460 Hz. Physical samples were then fabricated using 3D printing technology and experimentally tested for two variants of base partitions with different sound insulation performance. The obtained results showed a clear noise transmission reduction in the vicinity of the tuning frequency, reaching approximately 17 dB for the partition with a lower baseline sound insulation and approximately 10 dB for the more insulating partition. A dependence of the metamaterial effectiveness on the properties of the base partition was also observed. The results confirm that the proposed method enables a reliable assessment of the influence of metamaterial structures on the noise transmission reduction of partitions using small samples and a simplified measurement setup. Full article

This study addresses the impact of temperature gradient-induced non-uniform aging on the accuracy of space charge measurements in cross-linked polyethylene (XLPE) insulation for high-voltage direct-current cables. Existing pulse-echo acoustic (PEA) recovery algorithms neglect the evolution of material acoustic and dielectric properties during aging. To overcome this limitation, the systematic degradation of sound velocity, attenuation dispersion, and dielectric constant subjected to temperature gradient aging was experimentally investigated. Specimens were aged at temperatures ranging from 40 to 100 °C for durations up to 49 days. Then, quantitative models describing the dependence of acoustic and dielectric properties on aging severity were established. A space charge signal correction algorithm was then developed, incorporating nonlinear adjustments for sound velocity, attenuation, and permittivity according to the through-thickness aging profile. The algorithm’s accuracy was validated by comparing recovered charge waveforms and electric field distributions under 5 kV/mm for samples aged under different temperature gradients. The application of the method under high-voltage DC conditions revealed that aging induces non-monotonic changes in sound velocity, increased attenuation coefficients, and elevated low-frequency dielectric constants. Temperature gradient aging promotes heteropolar charge accumulation. This work provides a theoretical and methodological basis for improving the accuracy of the insulation condition assessment in long-term service HVDC cables. Full article

Taking a metro over-track TOD (Transit-Oriented Development) project in Chongqing as the engineering background, this study adopts a combined research approach integrating field measurements and numerical simulation. A coupled finite element model of the train–track–tunnel–soil–building system and a regional acoustic model are established to systematically reveal the vibration response characteristics of building clusters above the depot induced by metro operation, the propagation mechanism of structure-borne secondary noise, and the distribution patterns of the regional acoustic environment, while identifying the areas where vibration and noise exceed the prescribed limits as well as the key influencing factors. On this basis, following a hierarchical mitigation strategy consisting of source control, path interruption, and receiver protection, an integrated control scheme is proposed through the coordinated application of track vibration reduction, building vibration isolation, acoustic environment optimization, and building sound insulation. The engineering applicability and control effectiveness of the proposed scheme are further verified by numerical simulation. The findings of this study can provide theoretical support and technical reference for the refined design and integrated prevention and control of vibration and acoustic environments in similar metro over-track development projects. Full article

The work uses a comprehensive approach based on the information and communication concept of construction management templates to minimize information asymmetry between construction stakeholders when implementing innovative technologies. An analysis of the regulatory framework and patent research of existing analogs of wall structures was conducted. It was theoretically substantiated that the use of removable reusable formwork for monolithic walls made of expanded polystyrene concrete allows significant reduction in cost and logistics costs. A technology for erecting heat-insulating walls made of expanded polystyrene concrete (EPC) has been developed, which involves preliminary preparation of the insulation with the application of a protective reinforced layer. This allows avoiding performing labor-intensive and dangerous operations at height. A design of a noise-proof wall with sound-absorbing hollow-forming elements has been proposed, improving acoustic characteristics while saving materials. Thermophysical tests of fragments of walls made of expanded polystyrene concrete with a density of D250 (thickness of 260 mm) confirmed the need for additional insulation for heat transfer resistance for regulatory compliance. Acoustic studies have proven the effectiveness of using hollow-forming elements to increase the airborne noise insulation index and to reduce material consumption. All this helped to develop and patent the polystyrene concrete wall technology. For the first time, the concept of implementing the technological process of expanded polystyrene concreting of monolithic walls into construction management and production using construction management templates was proposed. This allowed the transformation of technological operations into a flow of objective data to minimize information asymmetry between project participants. It was theoretically proven that the objectification of production indicators through construction management templates is a base for measuring the commercial value and investment attractiveness of the technology being implemented. Full article