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We propose a novel hybrid acoustic metamaterial that can achieve broadband sound insulation below 452 Hz and almost perfect sound absorption at 864 Hz. The metastructure was fabricated using additive manufacturing. Finite element method simulations were used to study the acoustic properties of the fabricated metamaterials. An equivalent electrical circuit was built using an electro-acoustic analogy to evaluate the sound absorption coefficient. The unique design of this meta-structure possesses two resonant frequencies. Low-frequency sound insulation is found due to the effective negative density at frequencies lower than the cutoff frequency of the elastic membrane. In contrast, a negative effective bulk modulus is the reason behind the broadband sound absorption. The theoretical and simulation results were validated through experiments. Experiments carried out showed an overall average sound transmission loss of 26.31 dB between 50 and 1600 Hz and 24.72 dB in the low-frequency zone (<400 Hz). Furthermore, over 69% of the sound intensity is absorbed in the 500–1000 Hz frequency range. The designed meta-structure exhibits broadband effective negative density below 452 Hz and effective negative bulk modulus from 864 to 1220 Hz. The design specifies a sample thickness of 3.8 cm, corresponding to a subwavelength thickness of approximately λ/10. As a result, the developed meta-structure can potentially be employed for sound insulation and absorption at low frequencies in the aerospace and automotive industries and in-room acoustic applications. [ABSTRACT FROM AUTHOR]

In response to the increasing traffic noise problem, we designed a combined acoustic metamaterial (CAM) based on the multi-channel Fano resonance principle. By utilizing the Fano resonance coupling between the acoustic spiral structure and the hollow structure, efficient sound insulation under effective ventilation conditions is achieved. Simulation results of acoustic transmission loss show that the acoustic transmission loss of CAM is more than 13 dB in the frequency band of 520–989 Hz. The broadband sound insulation characteristic can block the oblique angle incident sound waves from different angles. Simulation results of the elastic strain energy and acoustic pressure field validate the sound insulation mechanism of the Fano resonance of the combined acoustic metamaterial. The experimental results in the impedance tube generally agree with the simulation results. To explore the possibility of wider engineering applications of CAM, we propose a combined CAM and CAM0.7 structure. The results show that a series structure of acoustic metamaterials can be selected to further realize broadband sound insulation within 500–1574 Hz. [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]

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]

Highlights Ultrasonic methods are more sensitive to defects such as voids, pores, and discontinuities that can diminish the true elastic and acoustic properties of materials compared to destructive testing. Therefore, the elastic properties and some acoustic properties of the epoxy phenol novolac modified with polystyrene (EPN‐PS) matrix‐based nano‐ and hybrid composites were determined for the first time using ultrasonic method. Montmorillonite‐type nanoclay (NC) and industrial red mud waste (RMW) at a rate of 1–4 and 15–35 wt% respectively, were used as fillers in the composite preparation. According to the results, the highest elastic coefficient values (L = 8.14 GPa, G = 1.76 GPa, K = 5.79 GPa and E = 4.80 GPa) were obtained in the EPN‐PS/NC1 (with 1 wt% NC) nanocomposite sample compared to the elastic properties of pure EPN and EPN‐PS, while the highest elastic coefficient values (L = 8.97 GPa, G = 2.19 GPa, K = 6.06 GPa, and E = 5.86 GPa) among hybrid composites (HC) were obtained for the HC35 containing 2 wt. % NC and 35 wt% RMW. Due to both its high elastic and good acoustic properties, wall panels and floors produced using HC35 hybrid composite can be used for sound insulation in noisy environments. First evaluation of the acoustic characteristics of epoxy phenol novolac modified with polystyrene‐nanoclay/red mud waste (EPN‐PS‐NC/RMW) composites. NC4 with 4 wt% nanoclay showed the lowest elastic and acoustic properties. Nanoclay ratio above 1 wt% reduces elastic and acoustic properties. The increasing RMW ratio in hybrid composites increases elastic properties. High elastic and acoustic properties make HC35 ideal for sound insulation. [ABSTRACT FROM AUTHOR]

This paper investigates the acoustic streaming effects (ASEs) and mechanisms behind the transmittance of sound in a metallic micro-cavity acoustic black hole (ABH) structure with an abrupt cross-section and examines the sound field flow characteristics inside the micro-cavity ABH under the sound excitation, such as the velocity, acceleration and pressure fields. And the sound transmission mechanisms are characterized by the ASEs which can be obtained by solving Navier–Stokes equations. The numerical results show that the sharp increase in the velocity and acceleration at the ABH tip position is the main reason for the focusing of the sound energy. And the dramatic increase in the tip cross-section reduces the acoustic streaming velocity, which is the main reason for the attenuation of the sound energy. Additionally, the thermoviscous effect of the acoustic boundary layer can also dissipate the low-frequency sound energy. The sound insulation experiment shows that the proposed micro-cavity ABH structure has a sound transmission loss (STL) of over 15 dB in the low-frequency regime. This research reveals the mechanisms of the ASE's work on the sound transmission properties of the micro-cavity ABH and provides new insight into low-frequency sound wave suppression. The ABH structure proposed in this paper has excellent strength, bearing capacity and long lifecycle, so it can be applied in the construction industry through its integrated design of structure and performance. [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]

The influence mechanism of waste rubber particles (WRPs) on the workability, mechanical properties, and sound insulation performance of recycled aggregate sound insulation mortar (RCM) were investigated. According to the principle of volume fraction replacement of recycled fine aggregate by 0 to 50%, WRPs with a particle size of 1–4 mm were incorporated in various mixtures of RCM. Each RCM mixture was tested for workability, mechanical, and sound insulation performance. Mercury intrusion porosimetry was used to analyze the distribution of pores and their sizes inside the material, and X-ray diffraction and scanning electron microscopy were used to analyze the characteristics of the interfacial transition zones (ITZs) between the rubber particles and the cement paste. The results showed that, owing to the hydrophobicity of WRPs, greater WRPs content led to greater fluidity of the mortar mix and a smaller water retention rate. Notably, the rubber in the mortar did not contribute to the hydration reactivity of the cement paste, but it changed the crystal morphology and pore structure of ITZ hydration products. The RCM incorporating 3–10% WRPs produced the optimal pore structure through the aggregate effect, which increased its overall compactness and mechanical performance. Further increase of WRP content significantly improved the sound insulation performance while significantly reducing the strength. Moreover, there was a clear logarithmic relationship between the strength and impact sound level index. This new knowledge can be used to prepare RCM that meets the actual strength and sound insulation requirements of the floor. Thus, the resource utilization of solid waste can be expanded. [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]

Optimization of impact sound insulation of wooden beam ceilings in Wilhelminian style houses, Part 2: Ceiling construction and flanking transmission The research deals with the influence of various parameters in the ceiling structure, such as cavity damping, screed thickness, impact sound insulation, fill and suspended ceilings, on the standard impact sound level of typical Wilhelminian style wooden beam ceilings. The measurements show that a thicker screed, softer impact sound insulation and a heavier fill significantly improve the impact sound level. Binding the fill with polyurethane instead of cement shows a significant improvement in the frequency range from 100 to 500 Hz. While cavity damping with mineral wool only contributes to a limited reduction in the standard impact sound level, decoupling the fill on an elastic intermediate layer delivers significant improvements. The measurements also show that the thickness of the paneling and the type of hangers in suspended ceilings have a significant impact on impact sound insulation. The investigations into flank impact sound transmission make it clear that flank transmission must be taken into account when planning higher requirement levels. Especially in the frequency range between 250 Hz and 800 Hz, the sound transmission of flanking components can play a significant role in the overall transmission. [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]

Polymeric wastes, specifically polyethylene terephthalate (PET) and scrap tyre rubber (STR), pose a significant environmental issue. PET, a thermoplastic polymer, is widely used in manufacturing bottles, PET cups, containers, fibres, films, and packaging materials. On the other hand, colossal rubber tyre waste quantities represent other environmental problems. However, PET and STR wastes are often discarded in the immediate vicinity, contributing to water resource pollution and landfill site strain. One solution is to replace aggregates in concrete mixtures with these wastes, a preferable alternative to landfill disposal because of the large volume and slow decomposition rate in landfills. Recycling PET and STR helps mitigate environmental pollution and promotes resource conservation and sustainability. This study aims to review previous research undertaken in the field and validate the findings of concrete’s fresh, mechanical, and functional characteristics. Based on the review, most studies confirmed a noticeable decline in the mechanical characteristics of mortar and concrete. However, these studies did not effectively focus on using PET and STR as sound and thermal insulation aggregates. Replacing PET and STR as aggregate in concrete can reduce thermal conductivity and acoustics. [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]

Copyright of German International Journal of Modern Science / Deutsche Internationale Zeitschrift für Zeitgenössische Wissenschaft is the property of Artmedia24 and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study deals with 3D printing multilayered micro-perforated panels (M-MPPs) coupled with buildings materials as compressed earth block for noise reduction applications. The sound absorption coefficient α is utilized as a metric to assess the sound insulation capabilities across a frequency range spanning from 10 to 3000 Hz, then evaluated and validated by numerical and experimental methods. The FEM model developed makes it possible to predict the acoustic absorption of M-MPPs by tuning the frequency range and varying optimized acoustics parameters, considering hole-hole interaction and taking into account visco-thermal effects that are present in compressed earth blocks. It is shown that the shape of perforations and material properties including the porosity rate, arrangement in the design of multilayer micro-perforated structures are identified to play a significant role in the sound performance of the entire structure. In addition, the application of MPP coupled with compressed earth blocks improve the sound absorption capacity of the composite structure. The developed FEM leads to accurate prediction of performance, efficient optimization, and cost effectiveness. Finally, the present study reveals the importance of M-MPPs combined with compressed earth blocks (CEBs) as viable noise reduction materials, particularly relevant for engineering applications and development initiatives in emerging economies. [ABSTRACT FROM AUTHOR]

Copyright of Automobile Technology is the property of Automobile Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

In this study, we experimentally demonstrate a class of lightweight acoustic metamaterial barriers that block low-frequency sound. The acoustic metamaterial barrier is composed of a thin rubber membrane coated over a stiff honeycomb plate. Our findings, combined with high-fidelity finite element simulations, demonstrate that the sound insulation performance of the acoustic metamaterial surpasses the mass law in three distinct frequency ranges: (a) the stiffness law dominates insulation up to 140 Hz, (b) degeneracy and destructive superposition of high-order natural modes dominate within the frequency range of 300–500 Hz, and (c) destructive interference between high-order resonance and membrane resonance dominates in the frequency range of 800–1200 Hz. Notably, our study highlights the potential of high-order shear vibration of the periodic structure for the resonant bending waves of the honeycomb cell that coincide with the wavelengths of longitudinal sound waves in air, thereby offering new design guidelines for lightweight acoustic metamaterial barriers. This study reports for the first time the coincidence of high-order and membrane resonance modes within the honeycomb cell by employing an accurate finite element model and experimental validation. [ABSTRACT FROM AUTHOR]

The use of machines and technology in the industrial sector has led to noise pollution, which requires attention. The practice of noise control through soundproofing is closely linked to the use of various acoustic materials, whether they are synthetic or natural fibers. Natural materials are preferred for biocomposite reinforcement due to the design flexibility, eco-friendliness, sustainability, and ease of availability. Therefore, this research aimed to analyze the variation of grinting grass (Cynodon dactylon) composite material as damper with safe working distance from noise exposure. This experimental research was conducted using industrial grinding machine and damper from grinting grass as the object and composite material. The instruments used for measurement included an Impedance tube (sound absorption coefficient), a sound level meter (noise intensity), and a Surfer 13 noise mapping application. The data obtained were analyzed using the Wilcoxon test to determine the differences before and after the intervention. The results showed that the most effective composite had a 60:40 ratio with a sound absorption coefficient of 0.30. Before using damper, the highest noise intensity recorded was 106 dBA, which was reduced to 83 dBA. Safe working distance from exposure before damper was 6.1 meters, which decreased to 1 meter after the intervention. In conclusion, there was a significant difference in noise intensity (p = 0.000) and safe working distance from exposure (p = 0.001) before and after the use of grinting grass as damper [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]

Mass timber panels including cross-laminated timber (CLT), dowel-laminated timber (DLT), and nail-laminated timber (NLT) are used increasingly as floor slabs in mass timber buildings and hybrid timber buildings. The sound insulation performance of bare mass timber structural floors is insufficient due to their lightweight and relatively high bending stiffness. Floating concrete toppings are commonly applied for improved sound insulation performance with an elastic interlayer. The effect of different elastic interlayers and thickness of concrete toppings on improving the impact sound insulation performance was investigated experimentally according to ASTM standards in this study. The results showed that with the same elastic layer, thicker concrete toppings resulted in better impact sound insulation performance with a higher apparent impact insulation class (AIIC). However, by increasing the concrete thickness from 38 to 50 mm and to 70 mm, the improvement of AIIC between two thicknesses was only within 3, and a significant improvement up to 9 was observed with a 100-mm-thick concrete topping. In general, elastic interlayers with lower dynamic stiffness values performed better; however, the performance was product dependent though the apparent dynamic stiffness was measured using the same standard method. Moreover, with the same panel thickness and wood species, a bare DLT floor provided higher AIIC (35) than a bare CLT (21), but each mass timber floor with the same interlayer and floating concrete topping had the same impact sound attenuation performance. The ISO empirical prediction equation overestimated the impact sound attenuation of floating concrete toppings on mass timber floors. [ABSTRACT FROM AUTHOR]

With the requirement of green construction, the building envelope system urgently needs lightweight material with high sound insulation performance. In this study, a kind of plywood with furfuryl alcohol/multilayer graphene oxide (FA/MLGO) layer was prepared by lamination. The four-microphone impedance tube method measured the sound insulation to evaluate optimal process parameters. At the same time, the acoustic impedance, damping performance, interface microstructure, and chemical components were characterized to discuss the sound insulation mechanism of FA/MLGO as a shielding layer. It showed that the weighted transmission loss of plywood with different FA/MLGO layers was enhanced, and acoustic impedance increased while the acoustic radiation damping coefficient decreased. In addition, considering economic costs, the optimal preparation process was three layers with 0.5 wt.% MLGO concentration and 50 wt.% FA concentration, followed by curing for three h. The surface properties, micromorphology, and chemical composition results indicated that FA/MLGO layer formed more complex sound propagation paths in the plywood, thereby increasing the loss of sound energy inside. Thus, the sound insulation of the plywood was improved. [ABSTRACT FROM AUTHOR]

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]

When the structure size is reduced to the micro- and nano-scale, a new mechanoelectric coupling effect, the flexoelectric effect, cannot be ignored. The governing equations and boundary conditions for the sound insulation problem of thin plate acoustic metamaterial structure with the flexoelectric effects were derived by means of the variational principle. The sound insulation curves of thin plate mass blocks were predicted based on the Kirchhoff theory. The effects of flexural effects, geometric sizes and mass densities on the sound insulation performances of the structure were systematically discussed. The results show that, for the micro- and nano-scale structure sizes, the flexoelectric effect significantly increases the sound insulation valley values and peak frequencies of the sound insulation curves, so it is necessary to consider the flexoelectric effects. This work provides a theoretical basis for the research of noise control in MEMS. [ABSTRACT FROM AUTHOR]

Impact sound insulation in renovated Wilhelminian‐style buildings – Part 1: Problem statement and renovation options Gassner & Partner Baumanagement GmbH, in collaboration with TU Wien, conducted a study to optimize impact sound insulation in Wilhelminian‐style building renovations. Historical renovations lacked specific sound standards, causing resident disruption. The research varied parameters like screed thickness, impact sound insulation, aggregate, and suspended subceilings to assess impact sound protection per ÖNORM B 8115‐5. Initial analysis of three properties showed reasonable protection in existing wooden beam ceilings. Suspended subceilings significantly improved sound levels, with the spectrum adaptation value CI,50‐2500 crucial for higher classification. Measurements during multiple renovations demonstrated that these measures are reproducible and can exceed new construction standards, significantly enhancing living comfort in historic buildings. [ABSTRACT FROM AUTHOR]

The insulating performance of double windows. Investigations in the test stand and in practice Box windows are essential components of our architectural heritage and have proven themselves over centuries due to their good sound and thermal insulation properties over a long lifecycle. In the course of thermal improvements of the building envelope, often historical windows are replaced by industrially manufactured constructions. The main argument for this window replacement is the high heat transfer of box windows. However, for these historical windows, measurement results from the actual existing structures are not used; instead, normatively defined default values are employed and compared with the heat transfer of insulated glass systems. These default values are three to four times higher than the laboratory values of industrially manufactured windows. Furthermore, the energy consumption of different window constructions is not evaluated over the entire lifecycle, and ecological aspects such as sustainability and repairability are rarely considered in these calculations. [ABSTRACT FROM AUTHOR]

Ceramic nanofiber aerogels (CNFAs), built from ceramic fiber components, stand out for their multifunctional properties, including low density, low thermal conductivity, high porosity, compressibility, robust chemical stability, and resistance to high temperatures. The continuity of the building blocks overcomes the brittleness of ceramic aerogels and expands their applications, which makes them widely used in the fields of high-temperature thermal insulation, sound insulation, oil-water separation, seawater desalination, air filtration, and electromagnetic wave absorption. Among the current methods for preparing CNFAs, electrostatic spinning is a perfect method for producing reproducible micro-nanofibers. Direct electrostatic spinning combined with freeze casting makes it easy to prepare CNFAs with anisotropic properties, while chemical vapor deposition makes it easy to prepare aerogels with random structures. The method of solution blow spinning has advantages of high fiber productivity and low-voltage electric field relative to electrostatic spinning, and the atomic layer deposition depends on templates to produce films with formulated thickness. This review initially explores the fabrication methods of CNFAs, including electrostatic spinning, freeze casting, chemical vapor deposition, solution blow spinning, and atomic layer deposition. Subsequently, it delves into the novel applications of CNFAs in recent years in the fields of high-temperature thermal insulation, sound insulation, electromagnetic wave absorption, oil-water separation, seawater desalination, and air filtration. Moreover, the advancement of CNFAs with high-temperature thermal insulation, fire resistance, strong flexibility, and tensile properties opens up promising applications in aerospace, personal protective equipment, and flexible wearable devices in the future. [ABSTRACT FROM AUTHOR]

Long-span highway–railway double-deck truss bridges are mostly located in urban centers, where noise pollution and traffic safety issues have a great impact. The fully enclosed barrier has excellent sound insulation and windproof performance and has been widely used in double-deck truss bridges in recent years. However, the large volume and the low air permeability rate will affect the aerodynamic characteristics of the bridge, resulting in vortex-induced vibration (VIV). To analyze how the fully enclosed barrier influences the highway–railway bridge VIV performance, this study analyzes the Huangjuetuo Yangtze River Bridge, combined with the wind tunnel test and the numerical calculation method to study different variations of the static three-force coefficient, the change of VIV response, and its influence mechanism after setting the fully enclosed barrier. The results show that the static three-force coefficient of the double-deck truss bridge changes significantly, the drag coefficient increases, and the absolute values of the lift coefficient and the moment coefficient decrease after the fully enclosed barrier is set. The aerodynamic performance of the bridge is significantly reduced after the fully enclosed barrier is set, and the amplitude and range of the VIV response are increased. Vertical bending VIV increased by an average of 58.5%, and torsional VIV increased by an average of 21.9%. Considering driving comfort and safety, attention should be paid to the double-deck truss bridge with a fully enclosed barrier. [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]

In this paper two waste fillers, namely ground tire rubber (GTR) and coffee silverskin (CSS, a waste bio‐product from the coffee‐making process), have been used to produce sustainable ethylene‐propylene‐diene monomer (EPDM) rubber compounds vulcanized on steel sheets to fabricate rubber‐to‐steel bonded systems for industrial roofing applications. The compounds have shown good mechanical performances, with elastic moduli in the range of 13–16 MPa, tensile strength of 13–20 MPa and elongation at break >400%, and strong adhesion to the metal substrate. Moreover, the rubber‐to‐steel bonded systems present good sound insulation properties (mean sound transmission loss [STL] of 39 dB and noise level reduction in simulated hailstones impact tests of 62 dB with respect to bare steel 73 dB). Accelerated UV‐ and thermal‐aging tests have shown excellent adhesion of the compounds to the metal substrate with the CSS acting as an antioxidant agent preventing excessive polymer degradation. The selected waste‐derived materials result in promising fillers for more sustainable rubber compounds. Highlights: Waste fillers were used to produce sustainable rubber compounds.Rubber‐to‐steel bonded systems for roofing applications were produced.Rubber‐to‐steel bonded systems have good sound insulation properties.Rubber‐to‐steel bonded systems have excellent adhesion.Coffee silverskin filler acts as an antioxidant agent. [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]