Search Results (665)

While polyurethane acoustic foam is widely used in entertainment settings for sound absorption, it poses a considerable fire risk when exposed to sparks from pyrotechnic devices. Even though fountain-type pyrotechnic devices are often perceived as producing “cold sparks”, the ignition potential of a single incandescent particle remains insufficiently quantified. This study experimentally investigates the ignition capacity of a fountain-type pyrotechnic article on pyramidal polyurethane acoustic foam under controlled conditions. Three dedicated experimental configurations were developed: (i) ignition probability tests at various distances, (ii) scaled configuration tests reproducing realistic installation geometry, and (iii) high-speed visualization of single incandescent particle interaction with the foam surface. For the first two configurations, ignition probabilities of 20% and 22.2% were obtained. High-speed recordings showed two distinct interaction mechanisms: particle fragmentation and ricochet, which did not result in ignition; partial penetration with localized melting, volatile release, and gas-phase ignition when residual thermal energy (about 0.5–1 J) was retained. The results demonstrate that even isolated single incandescent particles generated under realistic conditions can initiate the combustion of polyurethane acoustic foam. These findings challenge the “cold spark” safety perception and provide quantitative evidence that particle–induced ignition represents a significant fire hazard in enclosed environments where combustible acoustic materials and pyrotechnic effects coexist. The findings in this paper have direct implications for safety regulations in entertainment venues. Full article

Mycelium-based composites (MBCs) have already been applied in various fields, like construction, architecture, packaging, waste management and many others, as sustainable replacement materials. The composites created from such materials are lightweight, biodegradable and can take many different geometrical shapes. As there are many different combinations of fungal mycelium and organic substrates, it is not only important to investigate and determine which of these combinations perform best from an acoustic perspective but also from an environmental point of view. The sound absorption qualities of these biocomposites have been investigated. It was found that the sound absorption coefficients range from 0.33 to 0.49 in the mid-high frequency range for the four different mixtures of substrate and oyster mushroom (Pleurotus ostreatus). The results from the acoustic testing are promising, but the environmental impact of these mycelium-based composites also needs to be determined. The impacts from water and especially from energy, used during the growth and preparation cycles, are the main contributors to the environmental impact of MBCs, which is also confirmed by the relevant literature. A cradle-to-grave life cycle assessment (LCA) was conducted, utilizing the ReCiPe method, with selected environmental impact categories, based on real-world production data and the scientific literature. The results obtained were also compared with a commercially produced acoustical stone wool panel. The influence on environmental impact of the different substrates is also analyzed, determining which MBC is the most environmentally friendly and has the best acoustical properties. Full article

The use of agricultural waste fibres and natural binders is being investigated as alternatives to synthetic indoor acoustic materials. However, few studies have compared the fibre type, biopolymer type, and fibre-to-binder ratio for both sound absorption and sound transmission within a single controlled composite system. This study investigated the acoustic performance of sugarcane fibre (SF) and coconut fibre (CF) with a fixed thickness of 20 mm and density of 200 kg/m³, mixed with cassava, corn and potato starch binders with fibre–binder ratios from 1:1.0 to 1:0.1. Sound absorption coefficient was measured with an impedance tube, according to ISO 10534-2, and the sound transmission coefficient was determined using a four-microphone impedance tube system, according to ASTM E2611. Porosity was also tested for its relation to acoustic behaviour. The results showed that the coconut fibre composite recorded higher peak absorption, including α = 0.95 for cassava 1:0.6 to 1:0.7 and corn 1:0.6, while sugarcane fibre showed stronger transmission resistance, with SF-CAS-200-1:0.3 decreasing from τ = 0.11 at 160 Hz to 0.02 at 5000 Hz, and SF-PT-200-1:0.4 from τ = 0.10 to 0.03. The highest porosity values were 85.29%, recorded for SC-CAS-200-1:0.1, and 84.13% for CF-CAS-200-1:0.1. Overall, sugarcane fibre composites offered the best balance of absorption and low transmission, indicating strong potential for sustainable indoor acoustic panels, such as ceiling linings and wall systems. Further research should evaluate mechanical strength, fire performance, durability, and moisture resistance to support practical building applications. Full article

The durability of limestone aggregates is a critical factor affecting the long-term performance of concrete, particularly under aggressive environmental conditions. However, conventional durability tests such as the magnesium sulfate soundness test are time-consuming and labor-intensive. In this study, a transformer-based deep learning model, namely the FT-Transformer, was employed to predict the magnesium sulfate soundness loss of limestone aggregates using standard aggregate index properties. The dataset used in the modeling stage consisted of 108 limestone aggregate samples, each characterized by particle density, water absorption, Los Angeles fragmentation, and magnesium sulfate soundness loss. Although four standardized laboratory tests were conducted for each sample, yielding 432 individual test results in total, the prediction dataset comprised 108 complete observations. The predictive performance of the FT-Transformer was evaluated and compared with Linear Regression, Polynomial Regression, and Support Vector Regression models. Under the single-split evaluation, the FT-Transformer achieved a test $R^2$ value of 0.6473 and a test MSE value of 0.0212. In addition, a repeated random-split statistical analysis demonstrated that the FT-Transformer achieved better average predictive performance than Linear Regression across 50 repeated train, validation and test partitions. These findings indicate that transformer-based tabular learning can provide an effective and practically applicable framework for aggregate durability prediction and may support preliminary material assessment and engineering decision-making processes. Full article

Noise pollution poses significant challenges to human health and quality of life; thus, high-performance damping materials are attracting increasing attention. Rubber has been extensively applied in these materials due to its viscoelasticity. However, the damping performance of these materials is often constrained by the intrinsically limited energy-dissipation capability of the polymer backbone, which lacks sound-absorbing functionalities. Herein, a cross-linked sliding graft copolymer (SGC) was incorporated into isobutylene-isoprene rubber (IIR) and chlorinated butyl rubber (ClIR) to fabricate high-strength damping elastomers. Unlike conventional covalently cross-linked polymers, the cross-linked SGC features mobile junctions, which can slide along the polyrotaxane backbone to redistribute and equalize chain tension, giving rise to the “pulley effect”. Benefiting from the intrinsically high energy-dissipation capability of SGC and the cooperative contribution of interfacial hydrogen bonding, the obtained SGC/IIR and SGC/ClIR blends exhibit both enhanced damping performance and mechanical properties. The synergistic improvement in damping capacity and mechanical robustness renders the SGC/rubber blends as promising candidates for advanced sound-absorption applications. Full article

Earth has long served as a primary construction material because of its easy availability and low environmental impact. However, reliability of this material depends on the stabilization to enhance its strength, durability, thermal and acoustic performance. This study investigates the structural and environmental suitability of stabilized Dhahran soil in sustainable consruction. The soil samples were collected from the Eastern Province of Saudi Arabia and stabilized using cement and lime at dosages of 2.5%, 5%, 7.5%, and 10%. Experimental evaluations included unconfined compressive strength (UCS), durability under wet–dry cycles, thermal conductivity, and sound absorption. Results revealed that 10% cement stabilization achieved a UCS of 6.1 MPa after 28 days, while lime-stabilized samples failed to meet the 2 MPa structural threshold. Durability tests showed that as little as 5% cement provided sufficient resistance, with minimal weight loss under repeated cycles. Cement-stabilized specimens exhibited higher sound absorption at low frequencies, whereas lime-based mixes offered more balanced broadband performance. Thermal conductivity (TC) increased moderately with higher cement content, ranging from 0.311 to 0.388 W/m·K, reflecting improved densification and heat transfer efficiency. Overall, the findings demonstrated that Dhahran soil, when cement-stabilized, becomes a durable, structurally viable, and environmentally suitable building material, supporting its potential as a sustainable construction solution in arid regions. Full article

Noise pollution has become an increasingly discussed environmental problem in recent years. Developing a traffic infrastructure and recent sustainability goals require new solutions to mitigate noise pollution. This paper investigates the efficiency of the noise barrier made entirely of recycled materials. This solution would help achieve the United Nations sustainable development goals (SDGs). The proposed barrier target SDGs are: Good Health and Well-being (SDG 3); Industry, Innovation, and Infrastructure (SDG 9); Sustainable Cities and Communities (SDG 11); Climate Action (SDG 13). The changed barrier parameters were the parameters of the perforated panel and the air gap behind the porous material. To solve the optimisation problem, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method was used. The results showed that the proposed barrier configuration was the following: perforation shape—round, perforation diameter—5 mm, increment angle perforation—30°, thickness of the perforated panel—10 mm, porous absorbing material (composite rubber granule and hemp shive panel (RGHS))—50 mm thick, 20% of hemp shive content, air gap between absorbing material and the rigid backing—100 mm. The total thickness of the noise barrier was 180 mm. The acoustic parameters of the noise barrier structure were: α_avg. = 0.24, peaking at 0.51 (1250 Hz) and R_W = 39.7 ± 1.0 dB. These results indicate that the proposed barrier made of recycled materials could be a sustainable alternative for noise pollution mitigation and improving people’s quality of life. Full article

To address the current absence of targeted gradation design for porous asphalt pavements both domestically and internationally, this study employs the Coarse Aggregate Void Filling (CAVF) method to design the gradation of porous asphalt mixtures. Marshall stability tests, rutting tests, and scattering tests were conducted to investigate the relationship between coarse aggregate proportions and the structural stability of the mixture skeleton. An orthogonal experimental design was further utilized to examine the influence of three levels of fine aggregate gradation on the acoustic absorption characteristics of the mixture, and to analyze the effects of aggregate gradation on the primary pore diameter, connected pore diameter, and connected pore length. The results indicate that the coarse aggregate gradation predominantly governs the skeleton strength and overall pavement performance of the mixture, whereas the fine aggregate gradation exhibits significant effects on the interconnected void ratio, pore structure, and sound absorption performance. The optimal roughness range of coarse aggregates in porous asphalt mixtures is determined to be 0.46–0.52. The proportion of 0.6–1.18 mm aggregates has a pronounced influence on the primary pore diameter, connected pore diameter, and connected pore length. By integrating the design considerations for both coarse and fine aggregate gradations, a recommended gradation range for porous asphalt mixtures is proposed that achieves a balance between pavement performance and sound absorption/noise-reduction effectiveness. Full article

Underwater acoustic coatings are widely used to suppress low-frequency noise radiation and sonar reflection in underwater vehicles. In this study, an underwater acoustic coating model consisting of viscoelastic rubber layers and micro-perforated panel (MPP) structures is investigated, with particular emphasis on the low-frequency sound absorption mechanism and predictive modeling. Based on an improved transfer function method, a novel Micro-Perforated Panel Acoustic Coating Layer (MPPACL) model is developed to describe the coupled acoustic behavior of multilayer coatings under underwater conditions. The low-frequency sound absorption performance is primarily governed by the viscoelastic characteristics of the rubber layer, including material damping and complex modulus, while the incorporation of the MPP further enhances absorption through resonance effects. To efficiently explore the relationship between structural parameters and acoustic response, an ensemble learning-based deep neural network (ELDNN) is constructed using analytically generated data, enabling both forward prediction of sound absorption performance and inverse prediction of structural design parameters. The results show that the frequency prediction accuracy of the IDNN model is 3.7 times that of the DNN model. Furthermore, the proposed MPPACL model has achieved a significantly enhanced sound absorption effect within the frequency range of 50 to 2000 hertz. This effect has also been further verified through underwater experiments. The proposed framework provides an efficient and reliable approach for the design and optimization of underwater acoustic coatings. Full article

This study proposes a novel coplanar spiral-varying-channel space-coiled acoustic metamaterial (CSV-SCAM) for efficient low-frequency noise control in the range of approximately 200–400 Hz. By integrating continuously graded spiral channels with secondary spiral branches, the proposed structure enables multi-stage acoustic impedance matching and enhanced thermo-viscous dissipation, effectively overcoming the bulkiness and limited low-frequency efficiency of conventional porous absorbers. Finite element simulations and impedance tube experiments demonstrate that the CSV-SCAM achieves near-unity deep-subwavelength sound absorption, with a peak sound absorption coefficient exceeding 0.99 around 750–850 Hz using a thickness of only 10 mm. Furthermore, hybrid configurations composed of units with different branch numbers significantly broaden the effective absorption bandwidth by more than 20% while maintaining high absorption levels. Compared with traditional Helmholtz resonators, the proposed metamaterial exhibits superior compactness, structural robustness, and design flexibility, providing a promising solution for practical low-frequency noise mitigation in space-constrained engineering applications. Full article

Plastic pollution represents a significant challenge for the building industry, where synthetic foils are extensively used as acoustic absorbers or vapour barriers but persist in the environment for decades, causing risks to ecosystems and human health. In addition, conventional construction materials such as concrete and glass often provide poor acoustic performance, leading to a growing reliance on synthetic acoustic absorbers. In this study, we propose alginate—a biopolymer derived from brown seaweed—as an alternative sustainable material for indoor acoustic conditioning. Thin, bendable, and transparent alginate foils were fabricated and characterized in the impedance tube to assess their sound absorption properties. Results reveal that alginate foils achieve acoustic absorption coefficients comparable to conventional synthetic-based absorbers, while offering biodegradability and a renewable origin. Their physical properties further support potential integration into indoor architectural design, where flexible and transparent properties are desirable. Overall, the findings highlight alginate’s potential as an environmentally friendly replacement for synthetic acoustic foils, supporting the goals of acoustic sustainability and the associated long-term impacts of plastic pollution in the built environment. Full article

Airframe noise generated at wing trailing edges and high-lift devices, such as flaps, remains a major challenge during landing, with significant contributions in the low-frequency band of 500–1500 Hz. While solid surfaces reflect this acoustic energy, metallic porous materials can effectively absorb it through viscous and thermal dissipation within their internal pore structure. To address this, the present study examines the acoustic absorption characteristics of open-cell AlSi porous cylinders featuring controlled pore diameters between 0.3 mm and 2.25 mm. Measurements were conducted in an acoustic impedance tube according to the ISO 10534-2:2023 standard, using six cylindrical samples (28 mm diameter, 70 mm length). Two sets of measurements were performed for each sample (front and rear faces), and the average values were used. The findings indicate that the normal-incidence sound absorption coefficient α rises as pore size increases, reaching 0.93–0.97 at low frequencies of 500–700 Hz for the samples with the largest pores (1.8–2.25 mm). These results indicate that open-cell AlSi alloys offer strong low-frequencies sound absorption, positioning them as promising options for aeroacoustic noise mitigation, including applications such as porous trailing edge and hybrid flap designs. Full article

The upper atmospheric microwave sounding channels data are important for atmospheric data assimilation and retrieval. However, radiative transfer simulation accuracy is constrained by the precise characterization of the Zeeman splitting effect. This study investigates key influencing factors in upper-atmospheric microwave radiance simulations, focusing on the geomagnetic field parameters and the Zeeman splitting absorption coefficients. A three-dimensional (3D) atmosphere-magnetic coupling dataset is constructed using the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) version 2.0 Level 2A atmospheric profiles and the International Geomagnetic Reference Field (IGRF-13) as input for the microwave Line-by-Line (LBL) model. Observations from Special Sensor Microwave Imager/Sounder (SSMIS) channels 19 and 20 are used to quantitatively compare the effects of 2D and 3D geomagnetic fields on simulations and evaluate the impact of updated Zeeman splitting coefficients. Quantitative analysis reveals that the average vertical attenuation rate of geomagnetic field strength between 50 and 0.001 hPa is 2.98%, and using 3D magnetic field parameters improves the observation and simulation bias (O-B) for SSMIS channels 19 and 20 by approximately 3.67% and 3.52%, respectively. The updated microwave LBL model, incorporating molecular self-spin interactions and higher-order Zeeman effects, reduces the mean absolute error (MAE) and root mean square error (RMSE) of the SSMIS channel 20 by approximately 2.7% and 2.25%, respectively. Experimental results indicate that the 7⁺ line within a 2 MHz frequency shift is sensitive to moderate magnetic field strength (0.35–0.55 Gauss), while the 1⁻ line is sensitive to strong magnetic fields (0.5–0.7 Gauss). This study demonstrates that optimizing geomagnetic field representation and Zeeman splitting coefficients can improve upper atmospheric microwave radiance simulation accuracy by detailed comparison with observations. Full article

The treatment and management of waste in industrial processes remain a challenge, especially in material-intensive industries. In an attempt to mitigate this issue, sustainable architectural solutions focus extensively on the reuse of post-consumer waste in a bid to minimize environmental degradation. In this work, we propose a new acoustic metamaterial composed of three layers of reclaimed PVC diaphragms and a structured honeycomb core. The diaphragms were implemented on a hard frame in a manner that incorporates air gaps between layers and were tested using a portable impedance tube for setups including honeycomb panels behind diaphragms, in addition to setups including only air gaps, compared to diaphragms alone. The experimental and simulated results, using a transfer matrix approach, show a significantly improved low-frequency sound absorption performance within the 250–600 Hz band. Full article

This study investigates the synergistic use of Fischer–Tropsch wax (FTW) and recycled rubber powder (RP) as dual modifiers in stone mastic asphalt (SMA11) to improve its mechanical and functional performance. Rheological analysis demonstrated that an FTW content of 4% achieves the optimal balance of high-temperature rutting resistance, aging resistance, and workability, with a binder viscosity of 1.6 Pa·s at 135 °C. When incorporated into SMA11 mixtures at 15%, RP yielded the best overall mechanical performance, including a reduction in rut depth to 1.22 mm and a 25% decrease in wheel tracking slope (WTS). The 15% RP mixtures also exhibited superior long-term skid resistance (μ_m = 0.329 after 180,000 polishing cycles, corresponding to a 13% reduction in braking distance) and enhanced thermal cracking resistance (failure temperature improved by 8.0 °C to −32.7 °C). An RP content of 5% maximized moisture resistance (ITSR = 100%), while 10% RP produced the highest mid-frequency sound absorption coefficient (α = 0.050). The hybrid modification system enables a 20 °C reduction in production temperature, consistent with published data on wax-based warm-mix technologies, and is associated with reduced energy consumption and lower emissions. The approach simultaneously supports sustainable pavement design through the high-value reuse of waste tire rubber. Full article