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The imminent threat of noise pollution requires the development of efficient acoustic materials. Aerogels have been considered as a promising noise reduction materials due to their special porous structure, lightweight and acoustic delay characteristics. Currently, a variety of aerogels are investigated on materials, fabrication processes and structural design to explore the feasibility of aerogels as acoustic materials. This paper explains the acoustic mechanism for noise control, describes the mathematical models of sound absorption and insulation, as well as the preparation process of aerogels, and finally reviews the research progress and building application of aerogels in noise control. The future development of aerogels in noise control is also discussed. [ABSTRACT FROM AUTHOR]

Asphalt pavements are under extreme strain from high-volume traffic with ultraheavy axle loads, leading to rutting, fatigue, and moisture damage that reduces the useful life of asphalt mixtures. Studies have suggested that nanomaterials can be used in asphalt modification to delay asphalt pavement deterioration. The main objective of this research study is to investigate the influence of nanosilica aerogel (NSA) on the mechanical properties of hot-mix asphalt. The materials employed in the study include the 85/100 penetration grade asphalt binder, limestone aggregate, filler, and NSA additive in varying proportions of 1%, 2%, and 3% by asphalt binder weight. In order to evaluate the mechanical properties of the modified asphalt mixture, Marshall stability and flow, resilient modulus, moisture sensitivity, rutting, indirect tensile fatigue, and semicircular bending tests are performed. The results indicated that the range of 2 to 3% of NSA is a suitable limit for increasing the fatigue life, creep resistance, and strength of asphalt mixtures. Added NSA to asphalt mixtures can lead to a 40% increase in rutting resistance, an 80% increase in fatigue life, and a 12–15% increase in the stability of asphalt mixtures. In conclusion, the increase in aerogel improves the performance of uncracked asphalt mixtures and causes a slight decrease in the load leading to the fracture of cracked samples. Using NSA not only can lead to the creation of thermal, moisture, and sound insulation on the surface but also can lead to an increase in the stability, rutting resistance, and fatigue life of the asphalt mixture. [ABSTRACT FROM AUTHOR]

Lightweight double leaf walls have been extensively employed in assembly and large-space buildings. Due to the complex and varied stud configurations in double leaf walls, accurately and efficiently predicting the sound transmission loss (STL) of such structures poses a significant challenge. To support performance-based design workflows, this paper presents an analytical model based on sound transmission path decoupling, enabling architects to quickly predict the STL of commonly used lightweight double leaf wall types, including wooden, steel, and acoustical stud constructions. The paper systematically discusses the impact of different stud configurations on sound insulation performance and reveals the underlying mechanisms of sound bridge effects. Results show that the sound bridge effect arises from the structural sound transmission path introduced by various types of studs in the wall, and optimizing stud configurations is essential for decoupling the two leaves of the wall acoustically. Traditional wooden studs, considered as rigid frames, contribute more to the sound bridge effect compared to steel studs of the same structure. A promising approach involving acoustical studs with rubber sound isolation inserts is proposed, which achieves high-level sound insulation performance while offering significant spatial and construction efficiency advantages. This study provides valuable insights into advancing high-performance, lightweight building partitions and contributes to enhancing indoor soundscapes. [ABSTRACT FROM AUTHOR]

Silica aerogels are regarded as potential thermal and acoustic insulation materials with low density and porous structure. However, the hydrophilicity due to surface hydroxyl groups and the low mechanical intensity have limited its further application. Generally, it can be achieved by adjusting the process parameters of the sol-gel to refine the structure of silica aerogels and optimize performance. In this study, we adopted an appropriate modification strategy of incorporating glass fiber felts as the reinforcing phase and trimethylchlorosilane (TMCS) as the hydrophobic modifier. By adjusting the solvent exchange time, the micro-nano structure, i.e. hierarchical networks, was optimized. The TMCS-modified silica aerogel/glass fiber/hot-melt fiber composites (TSGMs) exhibited great sound insulation, and the maximum sound transmission loss (STL) was up to 34 dB at 6300 Hz. Compared to unmodified, STL improved by 8 dB in simulated practical applications. In addition, TSGMs also exhibited high hydrophobicity with a water contact angle of 147° and excellent thermal insulation with a thermal conductivity of 0.0345 W (m k)−1. The results could contribute to the refinement in the preparation process of silica aerogel composites and use in the fields of thermal and acoustic insulation. [ABSTRACT FROM AUTHOR]

With the waste of resources caused by human activities, it has gradually become an increasingly prominent social problem. The development of self-healing polymers in the field of insulation has attracted widespread attention. Develop polymer matrices with efficient healing efficiency and sound insulation properties to achieve green and sustainable resource conservation. In addition, improving the dielectric properties of intrinsic self-healing matrices has been a hot topic. In this work, we developed a new PEI matrix-modified self-healing polymer substrate that provides a breakdown field strength of 240 kV/mm and self-healing properties at room temperature, this has significantly improved the dielectric properties over other previously reported self-healing polymers. In addition to the abovementioned performance, we found significant differences in thermodynamic behavior in the synthesized end-modified polymers. By dielectric characterization (LCR), the breakdown composite can be left at room temperature for 60 min, and the material can recover 80 % of the initial properties without external intervention(This is demonstrated by the fact that its DC conductivity at 60 min of autonomous healing was significantly changed from that of the freshly electrically pierced DC conductivity and remained around 5.38 × 10−11 S/cm for a longer period of time thereafter). The microscopic morphology of the modified PEI matrix was observed by scanning electron microscopy (SEM) and EDS surface elemental analysis, which further supports the existence of metal coordination structures. These findings can further deepen the thinking of self-healing dielectric composites. The work inspired by this may break the limits and take self-healing composite dielectric materials to a new height. [ABSTRACT FROM AUTHOR]

The panel cavity structure is one of the key components of the aircraft (vehicle) body and is among the main noise transmission pathways. Based on the modal superposition and Galerkin method, this paper realizes the theoretical model of sound insulation of the clamped, double-panel structure. The non-dominated sorting genetic algorithm-II (NSGA-II) is used to realize the sound insulation of the clamped double-panel structure. Through optimization, the fitting function and law of structural surface density and the optimized normal weighted sound insulation Pareto fronts were obtained. The results show that among the optimization, for the Pareto front cases, their double-panel thickness ratio h 1/ h 2 is relatively far away from 1, and the corresponding cavity thickness H is relatively large. The influence of boundary conditions and size effects of lightweight sound insulation optimization are also discussed. The research on the influence of boundary and size indicates that the difference in the optimal weighted sound insulation Pareto fronts corresponding to the same surface density is mostly within the 1 dB range. Both the boundary and thickness of the panel will affect the frequency STL, while the boundary conditions or structure size changed, even the total thickness of panels needs to be the same, and the structure can also have similar weighted sound transmission loss (R w) when the thickness ratio of the double-panel structure is chosen properly. The difference of material effects is also discussed. This research provides a method for the sound insulation optimization of clamped double-panel structures concerning the boundary and size effect. [ABSTRACT FROM AUTHOR]

With increasing urbanization and industrialization, noise pollution has become a significant environmental issue. This study compares the sound insulation performance of two different sound barrier designs: water drop and trapezoidal. COMSOL Multiphysics software for computational simulations is used to calculate sound transmission loss (STL). The results indicated that the water drop design provides more effective sound insulation compared to the trapezoidal model. Additionally, economic analyses suggest that the water drop design may offer long-term advantages despite higher initial costs. [ABSTRACT FROM AUTHOR]

Mass timber is increasingly being employed in constructing low- and mid-rise buildings. One of the primary reasons for using mass timber structures is their sustainability and ability to reduce environmental consequences in the building sector. One criticism of these structures is their lower subjective sound insulation quality. Therefore, acoustic treatments should be considered. However, acoustic solutions do not necessarily contribute to lower environmental impacts or improved thermal insulation performance. This paper discusses a design methodology that incorporates the development of a sound insulation prediction tool (using an artificial neural networks approach), life cycle assessment analysis, and thermal insulation study. A total of 112 sound insulation measurements (in one-third octave bands from 50 to 5000 Hz) are utilized to develop the network model and are also used for the LCA and thermal insulation study. They are lab-based measurements and are performed on 45 various CLT- and ribbed CLT-based assemblies. The acoustic model demonstrates satisfactory results with 1 dB differences in the prediction of airborne and impact sound indices ( R w and L n , w ). An acoustic sensitivity study and a statistical analysis are then conducted to validate the model's results. Additionally, an LCA analysis is performed on the floor assemblies to calculate their environmental footprints. LCA categories are plotted against the acoustic performance of floors. No correlations are found, and the results emphasize that a wide range of sound insulation can be achieved with similar environmental impacts. Within each acoustic performance tier, the LCA results can be optimized for a floor assembly by selecting appropriate materials. The thermal insulation of floors is then calculated. Overall, a strong positive correlation is found between the total thermal resistance and heat loss against acoustic performance. Designers should be cognizant of the trade-offs between acoustic, thermal insulation, and environmental performance when choosing assemblies with favorable environmental impacts relative to acoustic and thermal insulation ratios. [ABSTRACT FROM AUTHOR]

The noise pollution issue along elevated urban rail transit lines has attracted considerable attention; however, research on the sound insulation characteristics of buildings during operational train noise remains limited. In this study, a field testing campaign was conducted in a building featuring facades constructed from aerated concrete blocks embedded with single-layer glass sliding windows along an elevated rail transit line. The sound insulation characteristics of the building were obtained based on measured data. By neglecting the influence of lateral sound transmission, a window-wall assembly model was proposed for simulating the building's sound insulation capability. To ensure the accuracy of the prediction results, initial simulations were first performed on individual elements and compared against the experimental sound insulation curves to identify key parameters. Subsequently, simulations of the window-wall assembly model were carried out and compared with test data to determine the acoustic boundary treatment. The results showed that the amount of sound insulation measured in the buildings ranged from 11.16 dB (A) to 19.85 dB (A) during train passage, exhibiting a notable dip in sound insulation within the frequency range of 80 Hz to 100 Hz. Conversely, the predicted sound insulation of 26.38 dB was much higher, also showing a significant dip at around 100 Hz. The simulated values aligned closely with the measured values below 500 Hz; however, discrepancies were observed in mid-to-high frequency ranges above this threshold. To this end, further simulations were performed on a window-wall assembly model incorporating air gaps to take into account air leakage effects. The results indicated that the presence of air gaps considerably diminished high-frequency sound insulation; when accounting for window air leakage effects, the simulated results approached closer alignment with the measured ones. [ABSTRACT FROM AUTHOR]

This study introduces a new method for fabricating biphasic architectured structures using self-developed hybrid material extrusion (MEX) process. This approach involves filling the voids of closed-cell structures with a powder material in a single process. The architectured structures were 3D printed using thermoplastic polyurethane (TPU) and subsequently filled with polyamide 12 (PA12) powder in two distinct configurations: partially filled (50%) and fully filled (100%), named as biphasic architectured structures. Experimental and numerical uniaxial quasistatic compression tests were conducted on partially filled and fully filled local and global closed-cell architectured structures, and their results were compared with those of empty architectured structures. The comparative analysis revealed that the partially filled structures, representing a transitional phase, exhibit enhanced properties which is influenced by the amount of powder filling within the structure. A substantial enhancement in stiffness and specific energy absorption (SEA) was observed in the consolidation phase. The fully filled architectured structures exhibit rapid increase in its loading response, characterized by high stiffness and SEA. Furthermore, this study paves the way for future exploration into strategic filling of multiple powders in different regions, thereby tailoring the mechanical and functional responses. Potential applications include manufacturing components and equipment that absorb energy, provide impact protection, and offer vibration damping and soundproofing capabilities. [ABSTRACT FROM AUTHOR]

This paper proposes a universal vibroacoustic coupling theoretical analysis model for investigating the sound insulation characteristic of corrugated core sandwich panel (CCSP) under different boundary conditions. The vibroacoustic coupling model consists of CCSP (structural field) and two three-dimensional acoustic cavities which simulate the incident sound field and accept the sound field, respectively. Based on first-order shear deformation plate and shell theories and acoustic theory, the dynamic model of CCSP and three-dimensional acoustic cavities are established by employing the differential quadrature finite element method in conjunction with the energy principle. The coupling of CCSP and three-dimensional acoustic cavities is realized by the velocity continuity condition at the acoustic–structure interfaces. The validation of the vibroacoustic coupling model is verified by comparing the results calculated by the established model with the corresponding results calculated by ABAQUS. The influence of model parameters on the vibroacoustic characteristic of vibroacoustic coupling model is investigated systematically for determining the critical structure parameters which have influence on the vibroacoustic behaviors. The effect of critical structure parameters on the sound insulation characteristic of CCSP is analyzed systematically for the optimization of the sound insulation performance of CCSP and provides theoretical basis and technique guidance. [ABSTRACT FROM AUTHOR]

Self-reinforcing porous mullite ceramics have attracted considerable attention in the field of insulation and sound absorption materials, due to their precise and controllable porous structure, high temperature and corrosion resistance, and low thermal conductivity. However, the high cost and relatively low performance obstruct their practical applications. In this work, self-reinforcing porous mullite ceramics were fabricated by utilizing construction waste via foam-gel casting and freeze-drying methods, and the impact of blowing agent dosage and sintering temperatures on the microstructures, sound absorption, and thermal insulation properties were systematically investigated. In addition, the related mechanism was also discussed in detail. The results show that, at a sintering temperature of 1000 °C and blowing agent dosage of 0.10 wt%, the self-reinforcing porous mullite ceramics can be successfully obtained, which exhibited a bulk density as low as 0.24 g/cm³ and porosity more than 90 %. Consequently, at a frequency of 2000 Hz, its absorption coefficient reached about 0.81. Furthermore, its thermal conductivity also decreased to about 0.06266 W/(m·K). This development not only unveils innovative avenues for the cost-effective fabrication of porous ceramics but also significantly broadens their potential applications within high-performance thermal insulation and sound absorption domains. [ABSTRACT FROM AUTHOR]

Sandwich structures possess a high stiffness-to-mass ratio, which facilitates flexural wave propagation at lower frequencies and enhances their vibration isolation and sound insulation capabilities, therefore, sandwich-like metamaterial plates with the nonlinear local oscillator is constructed in this paper to obtain adjustable bandgap in low-frequency. The buckling beam oscillator consists of a small mass, linear support spring, and buckling elastic elements for nonlinear stiffness. First, governing equations of flexural vibrations of plates are deduced based on the Hamilton principle. By utilizing the harmonic balance method (HBM), the dispersion relation of a sandwich-like plate can be determined. Theoretical analysis reveals the presence of structural bandgap ranges at lower frequencies, which are subject to the excitation amplitudes. And in order to validate the theoretical findings, the finite element method (FEM) is employed. Moreover, the influence of structural parameters, including oscillator mass, linear spring stiffness, buckling beam angle, and Young's modulus, are conducted to enhance the vibration control in the low-frequency. Interestingly, it is observed that the effectiveness of low-frequency suppression in the nonlinear metamaterial plate varies significantly across different boundary conditions. Therefore, the sandwich structures with nonlinear local oscillators can provide an effective way to suppress low-frequency vibration and maintain dynamic stability. [ABSTRACT FROM AUTHOR]

Polyurethane incorporated with nanofillers such as carbon nanotubes, basalt fibers, and clay nanoparticles has presented remarkable potential for improving the performance of the polymeric composites. In this study, the halloysite nanofiller-reinforced polyurethane elastomer composites were prepared via the semi-prepolymer method. The impact of different halloysites (halloysite nanotubes and halloysite nanoplates) in polyurethane composites was investigated. Scanning electron microscopy, X-ray diffraction, infrared spectroscopy, electronic universal tensile testing, and acoustic impedance tube testing were employed to characterize the morphology, composition, phase separation, mechanical properties, and sound insulation of the samples. The composite fabricated with 0.5 wt% of halloysite nanotubes introduced during quasi-prepolymer preparation exhibited the highest tensile strength (22.92 ± 0.84 MPa) and elongation at break (576.67 ± 17.99%) among all the prepared samples. Also, the incorporation of 2 wt% halloysite nanotubes into the polyurethane matrix resulted in the most significant overall improvements, particularly in terms of tensile strength (~44%), elongation at break (~40%), and sound insulation (~25%) within the low-frequency range of 50 to 1600 Hz. The attainment of these impressive mechanical and acoustic characteristics could be attributed to the unique lumen structure of the halloysite nanotubes, good dispersion of the halloysites in the polyurethane, and the interfacial bonding between the matrix and halloysite fillers. [ABSTRACT FROM AUTHOR]

A tremendous amount of waste black tea bags (BTBs) and date palm surface fibers (DPSFs), at the end of their life cycle, end up in landfills, leading to increased pollution and an increase in the negative impact on the environment. Therefore, this study aims to utilize these normally wasted materials efficiently by developing new composite materials for thermal insulation and sound absorption. Five insulation composite boards were developed, two were bound (BTB or DPSF with polyvinyl Acetate resin (PVA)) and three were hybrids (BTB, DPSF, and resin). In addition, the loose raw waste materials (BTB and DPSF) were tested separately with no binder. Thermal conductivity and sound absorption coefficients were determined for all boards. Thermal stability analysis was reported for the components of the tea bag (string, label, and bag) and one of the composite hybrid boards. Mechanical properties of the boards such as flexural strain, flexural stress, and flexural elastic modulus were determined for the bound and hybrid composites. The results showed that the thermal conductivity coefficients for all the hybrid composite sample boards are less than 0.07 at the ambient temperature of 24 °C and they were enhanced as the BTB ratio was reduced in the hybrid composite boards. The noise reduction coefficient for bound and all hybrid composite samples is greater than 0.37. The composite samples are thermally stable up to 291 °C. Most composite samples have a high flexure modulus between 4.3 MPa and 10.5 MPa. The tea bag raw materials and the composite samples have a low moisture content below 2.25%. These output results seem promising and encouraging using such developed sample boards as eco-friendly thermal insulation and sound absorption and competing with the synthetic ones developed from petrochemicals in building insulation. Moreover, returning these waste materials to circulation and producing new eco-friendly composites can reduce the number of landfills, the level of environmental pollution, and the use of synthetic materials made from fossil resources. [ABSTRACT FROM AUTHOR]

This paper explores the effect of waste rubber grain size on the porosity, modulus of elasticity, thermal properties, and soundproofing performance of polymer composites with different thicknesses (10, 15, and 20 mm). All properties were tested in accordance with European standards, with the exception of porosity, which was measured using Archimedes' principle. The findings indicate that with a consistent amount of polyurethane glue, finer rubber grains result in composites with higher porosity, leading to a lower modulus of elasticity but enhanced thermal and sound insulation. In contrast, coarser rubber grains produced composites with lower porosity and a higher modulus of elasticity, though with slightly reduced thermal insulation and significantly worse soundproofing. A combination of fine and coarse rubber grains provided a balanced performance, offering both good thermal and sound insulation while maintaining a high modulus of elasticity. Among the thicknesses tested, 15 mm was identified as optimal, combining a relatively high modulus of elasticity, low thermal conductivity, and better airborne sound insulation index. Future research will focus on applying this composite in concrete building products that meet noise protection and energy efficiency standards. [ABSTRACT FROM AUTHOR]

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As a type of locally resonant phononic crystal, alloy steel phononic crystals have achieved notable advancements in vibration and noise reduction, particularly in the realm of low-frequency noise. Their exceptional band gap characteristics enable the efficient reduction of vibration and noise at low frequencies. However, the conventional transmission loss (TL) simulation of finite structures remains the benchmark for plate structure TL experiments. In this context, the TL in the XY-direction of phononic crystal plate structures has been thoroughly investigated and analyzed. Given the complexity of sound wave incident directions in practical applications, the conventional TL simulation of finite structures often diverges from reality. Taking tungsten steel phononic crystals as an example, this paper introduces a novel finite element method (FEM) simulation approach for analyzing the TL of alloy steel phononic crystal plates. By setting the Z-direction as the excitation source, the tungsten steel phononic crystal plate exhibits distinct responses compared to excitation in the XY-direction. By combining energy band diagrams and modes, the impact of various excitation source directions on the TL simulations is analyzed. It is observed that the tungsten steel phononic crystal plate exhibits a more pronounced energy response under longitudinal excitation. The TL map excited in the Z-direction lacks the flat region present in the XY-direction TL map. Notably, the maximum TL in the Z-direction is 131.5 dB, which is significantly lower than the maximum TL of 298 dB in the XY-direction, with a more regular peak distribution. This indicates that the TL of alloy steel phononic crystals in the XY-direction is closely related to the acoustic wave propagation characteristics within the plate, whereas the TL in the Z-direction aligns more closely with practical sound insulation and noise reduction engineering applications. Therefore, future research on alloy steel phononic crystal plates should not be confined to the TL in the XY-direction. Further investigation and analysis of the TL in the Z-direction are necessary. This will provide a novel theoretical foundation and methodological guidance for future research on alloy steel phononic crystals, enhancing the completeness and systematicness of studies on alloy steel phononic crystal plates. Simultaneously, it will advance the engineering application of alloy steel phononic crystal plates. [ABSTRACT FROM AUTHOR]

Floor impact sound insulation is essential for improving living environments and has become a mandatory requirement for green buildings in Southern China. This study introduces an innovative inorganic sound insulation coating technology for enhancing building floor acoustic performance. Through comprehensive laboratory experiments and field tests, we evaluated inorganic coatings of 3 mm and 5 mm thickness, comparing their performance against traditional methods, including organic coatings and soundproof mortar. Standardized impact sound pressure level measurements, conducted in accordance with the China GB/T 50121 standard, demonstrated significant acoustic improvements. Laboratory testing revealed impact sound reductions of 6–7 dB and 9–10 dB for the 3 mm and 5 mm inorganic coatings, respectively, while field applications of the 3 mm coating achieved an average reduction of 14.3 dB. The inorganic coating exhibited superior performance characteristics compared to both organic coatings and soundproof mortar in terms of sound insulation efficiency, fire resistance, and application feasibility, demonstrating particularly effective attenuation in the mid- to high-frequency range. This investigation presents an innovative, cost-effective, and environmentally sustainable solution for improving floor sound insulation in green buildings. [ABSTRACT FROM AUTHOR]

Background: Several cognitive functions are related to sex. However, the relationship between auditory attention and sex remains unclear. The present study aimed to explore sex differences in auditory saliency judgments, with a particular focus on bottom-up type auditory attention. Methods: Forty-five typical adults (mean age: 21.5 ± 0.64 years) with no known hearing deficits, intelligence abnormalities, or attention deficits were enrolled in this study. They were tasked with annotating attention capturing sounds from five audio clips played in a soundproof room. Each stimulus contained ten salient sounds randomly placed within a 1-min natural soundscape. We conducted a generalized linear mixed model (GLMM) analysis using the number of responses to salient sounds as the dependent variable, sex as the between-subjects factor, duration, maximum loudness, and maximum spectrum of each sound as the within-subjects factor, and each sound event and participant as the variable effect. Results: No significant differences were found between male and female groups in age, hearing threshold, intellectual function, and attention function (all p > 0.05). Analysis confirmed 77 distinct sound events, with individual response rates of 4.0–100%. In a GLMM analysis, the main effect of sex was not statistically significant (p = 0.458). Duration and spectrum had a significant effect on response rate (p = 0.006 and p < 0.001). The effect of loudness was not statistically significant (p = 0.13). Conclusions: The results suggest that male and female listeners do not differ significantly in their auditory saliency judgments based on the acoustic characteristics studied. This finding challenges the notion of inherent sex differences in bottom-up auditory attention and highlights the need for further research to explore other potential factors or conditions under which such differences might emerge. [ABSTRACT FROM AUTHOR]

Aiming at the low-frequency line spectrum noise characteristics of power equipment noise, based on the principle of energy degradation, this paper combines the energy degradation sound insulation structure with the dynamic vibration absorption technology for the first time and applies it to the research field of noise control of power equipment in substations. Dynamic vibration absorption technology is used to effectively control low-frequency vibration and noise. Considering that there is an upper limit to the capacity of DVA, the sound-vibration energy degradation design of the transformer is completed by setting a sound insulation structure on the outside of the original transformer housing. It is analyzed that the vibration energy of the sound insulation structure in the specific frequency band is significantly reduced compared to the transformer housing, realizing efficient degradation of the vibration energy of the transformer housing and effective isolation of sound radiation. Through the optimized design of dynamic vibration absorption for the sound insulation structure, the structural sound isolation ability at the target frequency is further strengthened, and the system noise radiation level is greatly reduced under the action of multiple mechanisms at the target frequency, verifying the feasibility and high efficiency of the optimal DVAs energy degradation design of the transformer. [ABSTRACT FROM AUTHOR]

The aerogel performance for industrial uses can be tailored using several chemical and physical strategies. The effects of a controlled densification on polyurethane aerogels are herein studied by analyzing their textural, mechanical, sound, optical, and thermal insulating properties. The produced aerogels are uniaxially compressed to different strains (30%–80%) analyzing the consequent changes in the structures and, therefore, final properties. As expected, their mechanical stiffness can be significantly increased by compression (until 55‐fold higher elastic modulus for 80%‐strain), while the light transmittance does not noticeably worsen until it is compressed more than 60%. Additionally, the modifications produced in the heat transfer contributions are analyzed, obtaining the optimum balance between density increase and pore size reduction. The minimum thermal conductivity (14.5%‐reduction) is obtained by compressing the aerogel to 50%‐strain, where the increment in the solid conduction is surpassed by the reduction of the radiative and gas contributions. This strategy avoids tedious chemical modifications in the synthesis procedure to control the final structure of the aerogels, leading to the possibility of carefully adapting their structure and properties through a simple method such as densification. Thus, it allows to obtain aerogels for current and on‐demand applications, which is one of the main challenges in the field. [ABSTRACT FROM AUTHOR]

Slow rebound polyurethane foam (SPUF) has been widely used due to its advantages such as sound insulation, energy absorption, and good tactile sensation. However, SPUF is prone to harden at low temperature, and its application in medical equipment and households requires significant antibacterial properties. In this paper, self‐made silicone modified polyethylene glycol (Si‐APEG) and graphene oxide supported allicin (Alc@GO) were prepared and used as low‐temperature resistant agent and antibacterial agent, respectively. Low‐temperature resistant polyurethane foam (LSPUF) and antibacterial LSPUF (ALSPUF) were prepared respectively with water as foaming agent. The morphology of ALSPUF was observed by scanning electron microscope. Properties studied include apparent core density and porosity, mechanical properties including tensile strength, 40% compressive hardness, and rebound resilience, as well as low‐temperature resistance. Effects of Si‐APEG content on the structures and properties were analyzed and the LSPUF with an Si‐APEG content of 10 wt.% showed the best comprehensive performance. Therefore, ALSPUFs with Si‐APEG content of 10 wt.% and Alc@GO content of 0–3 wt.% were prepared. The addition of Alc@GO increased the antibacterial ratio significantly without obvious effect on the structure and mechanical properties of LSPUF. The antibacterial ratio of ALSPUF reached 99.07% at a Alc@GO content of 2.5 wt.% and testing time of 60 min. This work provides an effective and feasible method for the preparation of ALSPUF which can be widely used in medical devices and households. Highlights: Silicone modified polyether is a suitable low‐temperature resistant agent for PU foam.Allicin supported on GO provides good antibacterial property for PU foam.ALSPUF has better mechanical properties than SPU. [ABSTRACT FROM AUTHOR]

This paper presents a type of acoustic metamaterial that combines a labyrinth channel with a Helmholtz cavity and a thin film. The labyrinth-opening design and thin-film combination contribute to the metamaterial's exceptional sound-insulation performance. After comprehensive research, it is observed that in the frequency range of 20–1200 Hz, this acoustic metamaterial exhibits multiple sound-insulation peaks, showing a high overall sound-insulation quality. Specifically, the first sound-insulation peak is 26.3 Hz, with a bandwidth of 13 Hz and giving a transmission loss of 56.5 dB, showing excellent low-frequency sound-insulation performance. To further understand the low-frequency sound-insulation mechanism, this paper uses the equivalent model method to conduct an acoustic–electrical analogy, construct an equivalent model of the acoustic metamaterial, and delve into the sound-insulation mechanism at the first sound-insulation peak. To confirm the validity of the theoretical calculations, physical experiments are carried out by 3D printing experimental samples. The analysis of the experimental data has yielded results that are consistent with the simulation data, providing empirical evidence for the accuracy of the theoretical model. The material has significant practical application value. Finally, various factors are studied in depth based on the established equivalent model, which can provide valuable insights for the design and practical engineering application of acoustic metamaterials. [ABSTRACT FROM AUTHOR]

Honeycomb plates, due to their multi-cavity structure, exhibit excellent mechanical properties and sound insulation. Previous studies have demonstrated that altering the cell size and arrangement of honeycomb structures impacts their acoustic performance. Based on these findings, this study developed a wallboard structure with enhanced sound insulation by filling the cavities with paper fiber/cement facesheets and designing a stacked core structure. Through the reverberation chamber–anechoic chamber sound insulation experiment under 100–6300 Hz excitation and conducting orthogonal experiments from three dimensions, it was found that: (1) Compared to no filling, the filling with straw and glazed hollow bead can increase the sound transmission loss (STL) by more than 50% in the frequency bandwidth above 2000 Hz. This indicates that both types of fillings can significantly enhance the sound insulation performance of the honeycomb structure without a significant increase in economic costs. (2) The increase in paper fiber/cement facesheets improves the STL across the entire experimental bandwidth, with a maximum improvement exceeding 70%. This structural design not only offers superior sound insulation performance but also better suits practical engineering applications. (3) Increasing the number of core stacking units (from one to three), taking straw-filled paper honeycomb-core wallboards as an example, effectively increased the STL bandwidth. (4) This test enriches the application of honeycomb plates in sound insulation. Introducing fiber paper fiber/cement facesheets and eco-friendly, low-cost straw improves sound insulation and enhances the strength of honeycomb, making them more suitable for construction, particularly as non-load-bearing structures. [ABSTRACT FROM AUTHOR]

To reduce land use and avoid further pollution, incineration for power generation has become the main method for municipal solid waste treatment. This research focused on the potential for transforming Municipal Solid Waste Incineration Bottom Ash (MSWIBA) into a finely ground powder. The impact of the powder's fineness and the amount of water used on its effectiveness was analyzed using a method called grey theory. MSWIBA was used as a partial substitute for cement in making MSWIBA foam concrete and lightweight wall panels. By modifying the fineness and water utilization of the recycled micro-powder, its maximum activity index can be increased to 90.1. This study determined the influence of factors including apparent dry density, water–cement ratio, foaming agent dilution ratio, and admixture dosage on the strength of the recycled foam concrete, and established the optimal mix ratio. This study employed a combination of physical experiments and numerical simulations to elucidate the impact of panel material, core layer thickness, and layer sequence on sound insulation performance. The simulation results were in close agreement with the experimental findings. [ABSTRACT FROM AUTHOR]

A sandwich plate with a corrugation and auxetic honeycomb hybrid core is constructed, and its sound insulation and optimization are investigated. First, the motion governing equation of the sandwich plate is established by the third-order shear deformation theory (TSDT), and then combined with the fluid-structure coupling conditions, and the sound insulation is solved. The theoretical results are validated by COMSOL simulation results, and the effects of the structural parameter on the sound insulation are analyzed. Finally, the standard genetic algorithm is adopted to optimize the sound insulation of the sandwich plate. [ABSTRACT FROM AUTHOR]

The Stockholm Public Library was realized in two distinct phases of construction in the 1920s and early 1930s, and remains a well-known work in twentieth-century architecture, with a heritage status today. While previous studies have focused on the library's architectural design, particularly its lighting, acoustics were also an important aspect of the building's design and construction. This study marks the first detailed investigation of the library's architectural acoustics, with a suite of standard measurements performed to assess and characterize the library's historical room and building acoustics. Reverberation time measurements in the library's reading rooms yielded results of about 1.5–2 s for frequencies associated with speech. A significantly longer reverberation time of 5–6 s was measured in the library's central rotunda, confirming a prominent acoustic issue in the library, where appropriate heritage discussions are needed in the future as the library undergoes a major renovation in the coming years. A comparison of the measured airborne and impact sound insulation of the 1920s and 1930s reading room ceilings also yielded interesting results. While the materials in library's two construction periods are notably different, the airborne sound insulation performance of the 1920s and 1930s floors or ceilings was comparable and in line with contemporary standards. Impact sound insulation results from the 1920s and 1930s floors, however, differed significantly, with the latter displaying a relatively poor performance. Flanking transmission effects related to historical construction details and deviations from archival plans were investigated and discussed. This work emphasizes the practical and academic importance of conducting on-site measurements, and the close mutual development of modern architecture, construction, and architectural acoustics. [ABSTRACT FROM AUTHOR]

Residential homes and apartments' cooling and heating needs account for 63% of total building energy consumption. Improvements in the properties of building envelopes are among the best ways to reduce their energy consumption. The project's general objective was to compare the performance of externally insulated and traditional envelopes of light wooden frame buildings at full scale. Two houses were constructed and equipped with relative humidity sensors and temperature probes to assess the physical properties of the building envelope. The first house was built according to the conventional method (insulation between the studs), and the second house was built according to the method with the insulation outside the wall (also known as the perfect wall). The results showed that external insulation effectively mitigates internal condensation risks by relocating dew points to the exterior surface, thereby enhancing structural durability and thermal stability. Thermographic imaging confirmed reduced thermal bridging and improved thermal performance in the externally insulated walls. Overall, this study supports, with a full-scale experiment, the adoption of external insulation as a viable strategy for enhancing energy efficiency, thermal comfort, and durability in residential buildings. [ABSTRACT FROM AUTHOR]

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A topological interlocking assembly (TIA) is an assembly of blocks together with a non-empty subset of blocks called the frame such that every non-empty set of blocks is kinematically constrained and can therefore not be removed from the assembly without causing intersections between blocks of the assembly. TIA provides a wide range of real-world applications, from modular construction in architectural design to potential solutions for sound insulation. Various methods to construct TIA have been proposed in the literature. In this paper, the approach of constructing TIA by applying the Escher trick to tilings of orientable surfaces is discussed. First, the strengths of this approach are highlighted for planar tilings, and the Escher trick is then exploited to construct a planar TIA that is based on the truncated square tiling, which is a semi-regular tiling of the Euclidean plane. Next, the Escher-Like approach is modified to construct TIAs that are based on arbitrary orientable surfaces. Finally, the capabilities of this modified construction method are demonstrated by constructing TIAs that are based on the unit sphere, the truncated icosahedron, and the deltoidal hexecontahedron. [ABSTRACT FROM AUTHOR]

With the increasing demand for building acoustic performance, accurately evaluating the acoustic performance of building walls has become an important research topic. However, existing research has mostly focused on general building materials such as concrete, iron and steel, and glass. For wooden structure wall, due to the sound absorption performance of the materials themselves and the complexity of structural design, the analysis of their acoustic performance is still relatively weak. Moreover, there is a lack of quantitative description of their spectral characteristics and acoustic impedance. To analyze the acoustic performance of wooden structure building walls, Building Information Model (BIM) and impedance tube method were integrated to construct a building wall performance testing system with BIM technology. The impedance tube method was applied and testing functions for sound absorption and insulation performance were designed. The outcomes indicated that in the error test, the error range between the experimental group and the control group was [0.01, 0.18], indicating a high reliability of the experimental results. In the calculation of sound insulation of different specimens at different sound frequencies, when the frequency was 1600Hz, the sound insulation of the control group and experimental group was 65.30dB and 70.14dB, proving the effectiveness of the design method. The above results demonstrate the practicality of integrating BIM technology and impedance tube method in the acoustic performance analysis of wooden structure building walls. This study provides strong technical support for reducing the indoor environment of wooden buildings and improving the comfort of people's living environment. [ABSTRACT FROM AUTHOR]

Achieving ultra-low and ultra-broad-band sound absorption and full-band sound insulation is a major challenge. Here, we propose a composite structure of a multilayer micro-perforated plate and acoustic black holes to achieve this purpose. Combining the stable sound absorption effect of the multilayer micro-perforated plate in the full frequency band and the sound insulation effect of the acoustic black hole in the low frequency and the excellent sound absorption effect in the high frequency, the excellent sound control effect of 600–3150 Hz absorption coefficient greater than 0.8 and 100–3150 Hz sound transmission loss greater than 50 dB is achieved. The acoustic properties of different components and different acoustic black hole outlet were evaluated by finite element method, and the principles of sound absorption and insulation of the composite structure were elaborated. Finally, the results of finite element method are verified by impedance tube experiments. This work can make further progress in elucidating the acoustic properties of the ABH and open up new avenues in the control of ultra-low and ultra-wide frequency acoustic waves. [ABSTRACT FROM AUTHOR]

Building partition structures must meet several construction and technical parameters. During the measurement of the acoustic properties of dividing structures in real conditions, surprising results are often achieved that do not correspond to the expected values. Based on this reason, the composition of nine dividing constructions were designed. The measurements were carried out under conditions that are very close to real conditions. Measurements were performed in accordance with international standards. The monitored parameters also include acoustic parameters. In this paper, the analysis of acoustic parameters of nine building dividing structures (profiles) with different compositions was performed. The individual layers were made up of common building elements. Various statistical methods, variance analysis and regression were used in the evaluation. The apparent sound reduction index values measured for different profile types for frequencies from 100 to 3150 Hz are compared using Variance Analysis (ANOVA); the assumptions for their use are verified by the Shapiro–Wilk test and Levene Test of Homogeneity of Variances. Multiple linear regression was used to identify and analyze the relationship between the independent variables and the dependent variable. The methods of regression and correlation analysis were used in determining the parameters that affect the resulting coefficient of weighted structural sound insulation. The total thickness of the profile and the number of layers were found to be statistically significant parameters. Based on these analyses, the coefficient of weighted structural sound insulation was determined. A clear-cut definition and identification of the single-number rating required would thus be instrumental in selecting the appropriate material for accomplishing the desired objectives. [ABSTRACT FROM AUTHOR]

This article explores the use of cellulose and paper-based products in building acoustics. It examines various materials such as cellulose wool, paperboard, corrugated cardboard, and honeycomb panels, and evaluates their acoustic absorption and insulation properties. The results indicate that these paper-based products can be effective alternatives to traditional materials in terms of both absorption and insulation performance. The article emphasizes the potential of paper-based materials in reducing the environmental impact of the building industry. The text also discusses the resonance frequencies and properties of Helmholtz resonators and double walls with the insertion of Helmholtz resonators, providing equations and formulas to calculate their resonance frequencies and transmission loss. It describes the measurement methods used to assess the sound absorption and sound reduction properties of various materials, including cellulose and paper-based products, and presents the results obtained from these measurements. The document also discusses the dynamic properties of paperboard and the testing methods used to measure these properties, as well as the results of tests conducted on cellulose wool. It highlights the environmental benefits of using recycled materials like cellulose wool. The text provides data and analysis on the acoustic properties of various cellulose and paper-based materials used in building construction, including cellulose wool, paperboard, corrugated cardboard, and honeycomb panels. The measurements include parameters such as sound reduction index, sound absorption coefficient, and dynamic Young's modulus. The results demonstrate that these materials have different acoustic characteristics and can be utilized for sound insulation and absorption in [Extracted from the article]

The escalating demand for polyurethane rigid foams (PURF) has resulted in a substantial increase in waste polyurethane products. In view of the difficulty in recycling waste PURF, this study introduces a novel mechanical recycling process that is cost-effective and features a straightforward fabrication process for producing PUW (waste PURF combined with wood veneers), which solves the problem of low strength products obtained from mechanical recycling of PU waste. Through investigation of the PURF (ground into particles before using) particle size, core layer density, the amount of resin and thickness, the optimal fabrication process was confirmed as follows: particles with the size of 1 to 3 mm as its core layer components, 0.9 g/cm3 as its core layer density, the addition of MDI to be 20 wt%, and 8 mm thickness of whole composite. The resulting PURF-based composite exhibited superior thermal insulation properties, mechanical strength, and sound insulation performance. The optimized PUW composite had a notably low thermal conductivity of 0.04126 W/(m·K), slightly higher than that of rock wool board (0.04 W/(m·K)). In terms of mechanical performance, the wet shear strength of the optimal PUW composite reached 0.61 MPa. Furthermore, the PUW composite exhibited relatively high sound insulation, particularly at high frequencies. [ABSTRACT FROM AUTHOR]

Sandwich structures are widely used in various fields. Curved sandwich structures have attracted the attention of researchers owing to their superior stiffness and strength. With the application of the structures in engineering, it is required that the structures can not only meet the needs of mechanical loads but also can cope with thermal, acoustic, optical, and electrical loads. Sound insulation is one of the most common problems in the fields of aerospace, transportation, and architecture, so it is imperative to research new structures with good mechanical and acoustic properties. In this paper, a composite structure which is coupled with curve shell sandwich structure and acoustic metamaterials is proposed to obtain good mechanical and acoustic properties. Based on the harmonic expansion method and principle of virtual work, the theoretical model is established and the sound transmission loss (STL) performance is studied. Then, the effects of the geometry of the structure and material parameters on the STL of the structure are discussed. [ABSTRACT FROM AUTHOR]

Chiral metamaterials have been proven to possess many appealing mechanical phenomena, such as negative Poisson's ratio, high-impact resistance, and energy absorption. This work extends the applications of chiral metamaterials to underwater sound insulation. Various chiral metamaterials with low acoustic impedance and proper stiffness are inversely designed using the topology optimization scheme. Low acoustic impedance enables the metamaterials to have a high and broadband sound transmission loss (STL), while proper stiffness guarantees its robust acoustic performance under a hydrostatic pressure. As proof-of-concept demonstrations, two specimens are fabricated and tested in a water-filled impedance tube. Experimental results show that, on average, over 95% incident sound energy can be isolated by the specimens in a broad frequency range from 1 kHz to 5 kHz, while the sound insulation performance keeps stable under a certain hydrostatic pressure. This work may provide new insights for chiral metamaterials into the underwater applications with sound insulation. [ABSTRACT FROM AUTHOR]

Biowall is one of the several innovative strategies people use to build a comfortable interior atmosphere with living plants. This research attempts to trace the gaps in the previous analysis as a 'state of the art' with a literature review method by focusing on the biowall method, area ratio and types of plants. Biowall performance is mainly related to the influence of thermal, visual, audial, and respiratory comfort. It is an essential topic used to induce atmospheric interiors, such as temperature, humidity, light intensity, sound insulation and absorption, CO2, HCHO, VOC, and particulate levels. The results showed that the empirical methods used were actual scale-up and down experiments, laboratories in test chambers, simulation with specific software, and case research on in-situ biowall. The comparison between the biowall and room size varied significantly due to the absence of a legal basis and reasons. Ferns and succulents were the most widely used species to induce atmospheric comfort. Therefore, it is necessary to conduct further research on biowall physical comfort based on multisensory simultaneously and determine its standard dimension and digital integration. Subsequent researchers must further discuss home-scale biowall acceleration and utilization of food-medicinal plants. [ABSTRACT FROM AUTHOR]

The core layer is very important in studying the vibration and noise problems of sandwich structures. The present paper studied the free vibration and sound insulation characteristics of FG-CNTRC sandwich plates with FG-CNT face sheets and different cores including the soft core (epoxy), hard core (aluminum) and porous metal foam core with different porosity distributions. By Hamilton's principle the dynamic equations of FG-CNTRC sandwich plates are formulated based on the third-order shear deformation theory (TSDT), and the sound insulation expression is given under the excitation of the sound pressure. The theoretical solution of natural frequency and sound insulation are compared with the finite element simulation results and validated. The natural frequency of the square sandwich plate are compared with the rectangular case. The free vibration and sound insulation performance of FG-CNTRC sandwich plates are analyzed and discussed, and parametric studies are performed to evaluate the effects of CNT volume fraction, CNT distribution patterns, CNT orientation angles, porosity coefficient and incident angles on the vibro-acoustic characteristics of the sandwich plate. Some new results are presented to be used as references for the further research. [ABSTRACT FROM AUTHOR]

Modern science and technology constantly require new and novel materials with special properties. Over the past decade, Nanocomposites materials have received significant attention as active materials in components ranging from sensors to biomaterials, electronics devices to structural parts. These novel composites have applications in many areas, such as energy, insulation, manufacturing, and the modern building industry. However, not all applications have the same requirements in terms of acoustic insulation, so it is useful to adapt the kind of core materials and their product specifications, such as particle size and porosity, to the different applications. Furthermore, in some applications, cheaper core materials, like precipitated silica, would be a reasonable alternative to replace the time-consuming series of measurements. Because of many bad conditions that affect acoustic insulation properties in modern buildings. And to summarize recent applications of nanotechnology as they relate to textile fibers, yarns, and fabrics for improving acoustic insulation in modern buildings and civilian communities, this paper discusses the ability to apply 3D woven spacer fabric (3DWSF) composite materials reinforced with epoxy, rigid polyurethane foam, and silica nanoporous particles, which were prepared by the sol-gel technique. Four samples had been prepared, all of these samples were textile composite materials, and reinforced with two types of nano silica 99.8% SiO2; mesoporous Ns particles with porosity up to 83%, true density 0.08 g/cm³, and particle size between 100 and 2000 nm and pore size 70–150 nm, which had been prepared by Sol-gel technique, and nonporous Aerosil®200 particles with surface area 200–225 m2/g, true density 0.25 g/cm³, and particle size between 2 and 20 nm. We used rigid polyurethane foam as core material, and epoxy resin for laminating the fabric. 3D spacer E-glass fabrics, and chopped E-glass microfibers had been used. The weight percentage of silica nano particles which were used in this research was 5% by weight, which was better for economic reasons, and enough, to enhance the acoustic absorption coefficient up to R w = 99.79%. The best sound absorption could be achieved by using mesoporous silica nanoparticles, and soundproofing of an insulator using this porous structure is better than using a nonporous one. We found in this research that the thickness 45 mm and semi-porosity structure of the 3DWSF composite insulator material were enough to make a difference, with reference to the thermal and acoustic insulation guide of buildings. [ABSTRACT FROM AUTHOR]

A theoretical model of the normal sound insulation of a rectangular locally resonant (LR) plate with simply supported boundary conditions is established. The accuracy of the model is verified through comparison with finite element simulation results. Considering a 1-m2 aluminum plate as the research object, a non-dominated genetic algorithm is introduced. The algorithm optimizes the lightweight sound insulation of an LR finite plate with a center frequency band of 20–800 Hz as the optimization objective of maximum average sound insulation and minimum mass. The optimization parameters are substrate thickness and local resonance parameters (including resonator target frequency (f obj), number of resonators, additional mass ratio, and resonator damping). Optimization results indicate that the average sound insulation fluctuates at approximately 2 dB due to changes in f obj. The results also provide an optimal solution to the algorithm. The optimal sound insulation value curve of LR plates corresponding to different surface densities of intermediate improved cases is fitted and compared with the sound insulation value of an equal-mass bare plate. Under lightweight optimization, the resonators are deemed capable of improving the local frequency band sound insulation. In contrast, the wideband average sound insulation can approximate but not surpass the insulation provided by the equal-mass bare plate. In practical applications, an LR plate that can improve the local frequency band sound insulation and ensure the overall lightweight sound insulation performance of the wide frequency band can be obtained. This can be achieved by analyzing the frequency spectrum of optimal points in the lightweight sound insulation optimization process. Relevant research can provide a basis for the evaluation and design of the low-frequency sound insulation of plates for transportation equipment, such as airplanes, high-speed trains, and cars. [ABSTRACT FROM AUTHOR]

As promising candidates for widespread application, advanced ceramic fiber mats with robust mechanical properties are urgently needed. However, the brittleness, fatigue failure, and large density of ceramic fiber pose significant obstacles to its practical application. Herein, a novel SiO2 aerogel/ZrO2 composite nanofibrous membrane (SZCNFM) with excellent flexibility was prepared by introducing SiO2 aerogel nanoparticles into ZrO2 nanofiber via simple co‐electrospinning. The developed tetragonal zirconia phase without changing up to 1200°C endows SZCNFM material with excellent thermal stability. Furthermore, the as‐prepared membranes exhibit fatigue resistance ability which can maintain 98% of the original stress after 100 buckling cycle tests. The addition of mesoporous structure aerogel reduces the heat transfer of the nanofibrous membrane, giving its low thermal conductivity (30 mW/m/K) and low‐frequency sound absorption (noise reduction coefficient of 0.52). Combined with the high‐temperature resistance, low thermal conductivity and excellent sound‐absorption ability make it a promising material for heat insulation and acoustic absorption. [ABSTRACT FROM AUTHOR]

Middle and low frequency band sound waves have strong penetration and diffraction abilities during the propagation process, making it difficult to attenuate. The control of middle and low frequency broadband sound waves has become a challenging topic. Therefore, it is necessary to develop new materials or structures with middle and low frequency sound absorption, insulation, and noise reduction functions. The special properties of acoustic metamaterial provide new ideas for the development of sound absorption and insulation. In order to effectively control the noise in the lower frequency band, a new spatial spiral acoustic metamaterial was designed. First, the mechanism of band gap characteristics of a new spatial spiral acoustic metamaterial is analyzed. Then, a new spatial spiral acoustic metamaterial is completed through the finite element software COMSOL Multiphysics and the calculation and analysis of sound absorption and insulation performance in the 100–2500 Hz frequency band are completed. With the help of 3D printing, the preparation of metamaterial is completed, and the comparative experimental study of sound absorption and insulation performance of spiral acoustic metamaterial is carried out to verify the accuracy of the calculation method. [ABSTRACT FROM AUTHOR]

Windows are commonly the primary way for noise to enter the building environment. Most windows achieve higher sound insulation targets by simply increasing glass thickness or laminate. However, the glass thickness cannot be increased freely due to the window frame's limitation. This research selects eleven kinds of asymmetric insulating laminated glass (glass + polyvinyl butyral + glass + air + glass) within 27 mm, which are the typical thicknesses of window frames. The three pieces of glass have equal thicknesses. The half-space acoustics method investigated the acoustic properties and modal behavior of the glass with finite thickness. The results show that when PVB or three glass increases simultaneously, and the sound insulation of each glass can be improved by 0.9∼3.4 dB or 3.7∼21.8 dB at first resonant frequencies, respectively. The glass with the best sound insulation is 7 mm glass + 0.76 mm polyvinyl butyral + 7 mm glass + 5 mm air + 7 mm glass (7 + 0.76 + 7 + 5A + 7 for short). Its sound transmission loss (TL) is 38.5 dB from 125 to 4000 Hz and 16.8 dB in the first resonant frequency (200 Hz). In addition, its first resonant frequency is the highest among eleven kinds of glass, and the number of natural frequencies in the low frequency range is only 9. These findings can provide a basis for designing asymmetric insulating laminated glass to improve the low frequency noise reduction effect effectively. [ABSTRACT FROM AUTHOR]

Acoustic metamaterials (AMs) composed of periodic artificial structures have extraordinary sound wave manipulation capabilities compared with traditional acoustic materials, and they have attracted widespread research attention. The sound insulation performance of thin-walled structures commonly used in engineering applications with restricted space, for example, vehicles' body structures, and the latest studies on the sound insulation of thin-walled metamaterial structures, are comprehensively discussed in this paper. First, the definition and math law of sound insulation are introduced, alongside the primary methods of sound insulation testing of specimens. Secondly, the main sound insulation acoustic metamaterial structures are summarized and classified, including membrane-type, plate-type, and smart-material-type sound insulation metamaterials, boundaries, and temperature effects, as well as the sound insulation research on composite structures combined with metamaterial structures. Finally, the research status, challenges, and trends of sound insulation metamaterial structures are summarized. It was found that combining the advantages of metamaterial and various composite panel structures with optimization methods considering lightweight and proper wide frequency band single evaluator has the potential to improve the sound insulation performance of composite metamaterials in the full frequency range. Relative review results provide a comprehensive reference for the sound insulation metamaterial design and application. [ABSTRACT FROM AUTHOR]

This paper presents the initial prototypes of solutions designed using plastic caps, seeking acoustic applications for both airborne sound insulation and the acoustic conditioning of rooms. Plastic caps are a waste product from the packaging sector and they constitute a major waste problem, given that, if they are not attached to the packaging, they get lost during the recycling cycle and end up in landfill. Finding an application for this waste that can provide acoustic improvements is a sustainable alternative. This paper shows the results of airborne sound insulation measurements obtained in a scaled transmission chamber and sound absorption measurements obtained in a scaled reverberation chamber for different combinations of single and double plastic caps and combinations with thin sheets of sustainable materials, such as jute weaving, textile waste, hemp felt and cork board. Tests have shown that obtaining sound reduction index values of up to 20 dB is possible with plastic cap configurations, or even up to 30 dB is possible at some frequencies with combinations of caps and certain eco-materials. With regard to the sound absorption coefficient tests, close to unity absorption values have been achieved with the appropriate configuration at frequencies that can also be selected. The results indicate that these panels can be eco-solutions for airborne sound insulation as lightweight elements, or they can be used for the conditioning of rooms, tailoring the sound absorption maximums to the desired frequencies. [ABSTRACT FROM AUTHOR]