Search Results (41)

Currently, with the intensification of global education competition, how to cultivate innovative and versatile talents has become the focus of education today. Informal learning spaces (ILS) have received widespread attention due to their benefits for interdisciplinary interaction. Many forms of ILS have been built, and coffee shops are one of them. However, there is no uniform standard for the design of cafes as ILS, and there are many problems with the spatial quality. This study took a university cafe as a case study and conducted research on the environmental quality and influencing factors from the perspective of environmental behavior. In terms of research methods, this study adopted a combination of ultra-wideband positioning, questionnaire surveys, and environmental data measurements. This research method could obtain the complete relationship between user behavior, time, and location, which improved the shortcomings of traditional research methods of fragmented and accidental data acquisition, and helped to obtain more accurate research results. The study identified the impact proportions of four criteria layer elements and 26 scheme layer factors, which was also the main contribution of this study. In terms of four criteria layer elements, the physical elements had the highest proportion, accounting for 32.46%. The ontology elements ranked second, accounting for 27.07%. The atmosphere elements ranked third, accounting for 24.19%. Finally, facility elements accounted for 16.29%. The top three scheme layer factors were equipment and facilities, noise, and illumination, with weights of 11.18%, 10.71%, and 8.35%, respectively. The study summarized the development directions of cafes as ILS, such as considering the learning needs of different groups, installing sound-absorbing and soundproof devices, adding grilles to external windows, and improving glare problems. Full article

Thin sound-absorbing materials are particularly desired in space-constrained applications, such as in the automotive industry. In this study, we theoretically analyzed the structure of relatively thin glass wool or polyester wool laminated with a nonpermeable polyethylene membrane and a permeable nonwoven fabric sheet. We also measured and compared the sound-absorption coefficients of these samples between experimental and theoretical values. The sound-absorption coefficient was derived using the transfer matrix method. The Rayleigh model was applied to describe the acoustic behavior of glass wool and nonwoven sheet, while the Miki model was used for polyester wool. Mathematical formulas were employed to model an air layer without damping and a vibrating membrane. These acoustic components were integrated into a transfer matrix framework to calculate the sound-absorption coefficient. The sound-absorption coefficients of glass wool and polyester wool were progressively enhanced by sequentially adding suitable nonwoven fabric and PE membranes. A sample approximately 10 mm thick, featuring permeable and nonpermeable membranes as outer layers of porous sound-absorbing material, achieved a sound-absorption coefficient equivalent to that of a sample occupying 20 mm thickness (10 mm of porous sound-absorbing material with a 10 mm back air layer). Full article

Low-frequency noise absorbers often require large structural dimensions, constraining their development in practical applications. In order to improve space utilization, an acoustic metamaterial with a spatial double helix, called a spatial double helix resonator (SDHR), is proposed in this paper. An analytical model of the spatial double-helix resonator is established and verified by numerical simulations and impedance tube experiments. By comparing the acoustic absorption coefficients of the spatial double-helix resonator, it is shown that the results of the analytical model, the numerical model, and the experiments are in good agreement, proving the accuracy of the theoretical model. The effects of different structural parameters on the peak sound absorption coefficient and resonance frequency are quantitatively revealed. The impedance variation law of the model is obtained, and the resistance and reactance distributions at the resonance frequency are analyzed. In the optimization model, the Back Propagation (BP) network is used to construct the mapping between the structural parameters and the resonance frequency and sound absorption coefficient, and this is used as the constraints of the equation, which is combined with Wild Horse Optimization (WHO) to establish the BP-WHO optimization model to minimize the volume of the spatial double helix resonator. The results show that, for a given noise frequency, the optimized structural parameters enhance the space utilization without affecting the performance of the space double helix resonator. Full article

The motivation behind this study is to improve acoustic environments in living spaces using sustainable materials. This research addresses the challenge of enhancing the acoustic properties of sandwich structures through the integration of a honeycomb core with a membrane made from recycled materials, forming a recycled membrane honeycomb composite (RMHCC). The main objective is to develop a novel sandwich material with sound-absorbing characteristics suitable for real-world applications. The study employs both experimental methods and simulations, where a conventional hexagonal honeycomb geometry is combined with the recycled membrane to form the composite structure. A simulation model was developed to evaluate the effectiveness of the metamaterial in reducing reverberation time within a church setting. The results indicate that the RMHCC shows significant potential in improving acoustic performance, with a notable reduction in reverberation time even with minimal usage, highlighting its suitability for enhancing acoustic environments in various applications. Full article

In recent years, multi-functional lecture halls have developed rapidly and become a symbol of contemporary public spaces and places. This kind of spatial facility that brings together the advantages of land intensiveness and multi-functional integration also faces feedback such as poor acoustic effects. However, current research rarely involves the architectural design perspective, which is actually the root consideration of this problem; that is, how to set up corresponding spatial layout measures to optimize acoustic performance in a relatively economical and simple way. This study uses the academic lecture hall of the School of Architecture and Planning of Yunnan University as a case to try to solve these problems. The research is based on holistic considerations, starting from site selection, architectural design, aesthetic considerations, and environmental noise assessment, and combining simulation results with actual measurement results. Using a prediction–comparison–verification method, key acoustic parameters such as speech intelligibility, loudness, and reverberation time were calculated and evaluated to understand the acoustic design problems of the hall. The study found that the out-of-control reverberation time was the main cause of poor acoustic feedback, and based on this, optimization and transformation were carried out from an architectural perspective. Finally, a renovation suggestion was made that the application of sound-absorbing materials on the rear wall can achieve better acoustic effects inside the hall. Among the space combination methods, the combination of “rear wall, central ceiling, and front ceiling” has the best effect. Practical insights are provided for improving the acoustic performance of the multi-functional lecture halls while taking into account the acoustic design and feasible requirements. Full article

The automotive industry needs to improve energy efficiency rapidly to achieve carbon neutrality while creating a safe, secure, and comfortable driving environment for customers. Porous sound-absorbing materials and porous thermal insulators are typically used to satisfy these requirements despite limitations in mass and space. While these porous materials are similar, the microstructures they offer for high performance differ in the size and connectivity of their fluid phases, which enhances the difficulty of achieving excellent sound absorption and thermal insulation in the same material. In this study, a hydrophobic cellulose nanofiber–poly(methylsiloxane) xerogel composite was developed using computational microstructure modeling. This porous material has high porosity and excellent thermal insulation and sound absorption properties. Full article

This study aims to tackle the challenge of high noise levels on balconies while preserving natural ventilation. Eight innovative balcony designs, incorporating elements like diffuser edges, undulating ceilings, Helmholtz resonators, grooves, or sound traps, were evaluated via finite element (FE) modeling. The insertion loss results showed that for many balcony designs, noise reduction in the balcony could deteriorate beyond an elevation of 8 m. However, the front jagged and full wavy ceiling designs were shown to be more robust in noise attenuation across balconies on different floors. The jagged ledge and grooved parapet designs yielded an overall 1.5 dBA lower SPL at the exterior regions, compared to other designs, which implies that the designs are less acoustically detrimental to nearby residential blocks as they tend to diffract and absorb incident noise. The jagged ledge design is more effective for lower floors while the jagged ceiling design is more effective for higher floors. A combination of the protruded jagged ledge for the lower floor and jagged balcony ceiling for the higher floor would result in the lowest noise ingress over three stories of residential units: this would be capable of achieving more than 3 dB noise reduction and would offer viable options for improving balcony noise mitigation, by providing valuable insights to architects and designers seeking practical solutions for outdoor noise reduction. Our study highlights that whereas the spectrum characteristics of acoustic absorption materials may be less tunable, and where reduced head space is traded for thicker material for greater ab-sorption and added affixation and maintenance cost, the jagged ledge and ceiling curvatures can actually be shape-tuned, say for every 3 to 4 floors up the high-rise to more effective reduce noise ingress and possibly improve the architecture façade outlook. Full article

Variable acoustics systems are promising engineering developments for multi-purpose rooms and workspaces in many buildings. However, due to space requirements associated with most of the tuning devices used for that purpose, these solutions are hardly adopted in practice. In this work, two innovative tunable sound absorbers that cope with this drawback are proposed, one consisting of rotating perforated panels and the other being a panel with an iris-type aperture. Compared with conventional perforated panel sound absorbers, the designed solutions yield a variable open area ratio system, whose configuration allows tuning the absorption bandwidth without misusing space. To assess their sound absorption coefficient, impedance tube experiments were carried out following the standardized method described in ISO 10534-2 over specimens fabricated for this purpose using laser cutting and additive manufacturing technology. The results not only show their good sound absorption performance but also highlight their tuning capabilities. Complementarily, a model based on the ray tracing method was developed to evaluate the performance of these solutions in a case study room, for different occupancy levels, with the results supporting the previous assertions and revealing the improved intelligibility features when used in such scenarios. The proposed solutions, together with the prediction model, provide a feasible approach for the design and development of tunable sound absorbers in variable room acoustics. Full article

Many rooms struggle with the absorption of low-frequency sound due to its long wavelengths. The integration of existing solutions into these spaces is often challenging due to their intricate installations and large depths. To address this problem, a new type of resonance absorber has been developed: the Distributed Mode Absorber (DMA). It consists of a thin vibrating front panel and a volume of enclosed air behind it. This straightforward structure can be utilized to create acoustically functional furniture that can be seamlessly incorporated into rooms. This article is devoted to the structural optimization of the DMA front panel, using the Acoustic Black Hole (ABH) effect known within structural dynamics. A numerical model is constructed using a Finite Element Analysis (FEA) and examined numerically. Several geometric parameters of the ABH are studied with regard to their influence on the vibrations of the front panel. Prototypes are developed and manufactured based on these insights. The quality of the numerical model is verified during the subsequent validation. Finally, the sound absorption of the improved DMA is compared with that of the reference DMA. Full article

Recently, increased attention has been given to minimize the effects of noise pollution on living beings. The attenuation and manipulation of sound waves with low-frequency components are quite difficult with traditional absorbers due to inherent properties induced by large wavelengths and yet are particularly critical to modern designs. In this study, a parallel arrangement of a coiled-up space cavity and micro-perforated panel (MPP) is considered as the absorber configuration. The coiled-up space consists of a front panel with an orifice and a rigid backing panel enclosing an arch-shaped concentric channel. The entire coiled-up space length is provided with two varying cross-sections. By this arrangement, the sound path is squeezed into a reasonably small volume enabling sound absorption at low frequencies. A thin panel with numerous perforations is the main constituent of MPP. It is backed by an air cavity and terminated by a rigid backing. Here in this configuration, micro perforations are provided on the front panel of the coiled-up space, which ensures simultaneous entry of acoustic waves into the micro-perforations and coiled-up space structure. The absorption characteristics of the present configuration are studied numerically and analytically. The combined structure with parallel combination of coiled-up space and MPP resulted in the abatement of more than 70% of sound in the frequency range of 321 Hz to 853 Hz. The present absorber has only a 5.5 cm thickness, which is subwavelength$\left(\frac{\lambda }{19}\right)$ also. Full article

Aside from being a place for congregational prayers, the West Java Pusdai Mosque is also a center for preaching and other Islamic activities in West Java. Therefore, as a place of worship for Muslims, this mosque needs to maintain a comfortable atmosphere. The comfort or solemnity of worship can be affected by the noise of the surrounding environment or the acoustics of the room. This study aims to analyze the acoustic quality of the prayer room in the Pusdai Mosque, which is influenced by several factors. This research was conducted by observing and simulating, using the Ecotect v5.50 software. A simulation was carried out with the creation of a 3D model and the addition of both the absorption coefficient of the material in the room and speakers to it. In addition, research was also strengthened by conducting literature studies on scientific articles. The simulation was carried out to determine the reverberation time and sound distribution produced by the sound sources or speakers that could indicate the acoustic quality of the Pusdai Mosque. The acoustic quality of the Pusdai Mosque is greatly influenced by the interior materials and the shape of the ceiling. Based on the results of this analysis, the Pusdai Mosque has room acoustic defects. This is due to the large use of sound-reflecting materials and the form of the ceiling, which is quite complex. This causes a lot of sound reflection to occur, causing the reverberation time to exceed the optimum limit of a 500 Hz frequency (conversational space). This causes the speaker’s voice to become an echo or hum. Therefore, the Pusdai Mosque needs to improve its room acoustics in order to create comfort and solemnity in worship. Improvement can be made by adding sound-absorbing material. Full article

The reduction in CO₂ emissions has become an important issue as global environmental problems have become more serious. The replacement of conventional petroleum- and mineral-derived raw materials for building materials with local plant-based resources is expected to reduce CO₂ emissions. This study examined the possibility of using compression-molded boards made from plant-based resources as sound-absorbing materials in rooms. Among plant resources, few studies have conducted detailed measurements of the sound absorption properties of boards compressed from reeds. When measuring the normal incidence sound absorption coefficient, a material layered with a reed compressed board, wood fiber insulation, and an air layer showed a peak in the sound absorption rate at approximately 850 Hz. This indicates the potential to effectively absorb noise in the frequency band of human voices (500–1000 Hz). By changing the layering of multiple sound-absorbing materials, the presence or absence of an air layer behind them, and the installation conditions of the sound-absorbing materials, and then measuring the sound absorption rate, variations were observed in the sound absorption rate and the frequency at which the peaks were observed. This provides guidelines for material configurations that exhibit sound absorption at specific frequencies. Full article

One of the uses of Helmholtz resonators is as sound absorbers for room acoustic applications, especially for the low frequency range. Their efficiency is centered around their resonance frequency which mainly depends on elements of their geometry such as the resonator volume and neck dimensions. Incorporating additional necks on the body of a Helmholtz resonator (depending on whether they are open or closed) has been found to alter the resulting resonance frequency. For this study, tunable Helmholtz resonators to multiple resonance frequencies, are proposed and investigated utilizing additional necks. The resonance frequencies of various multi-neck Helmholtz resonators are first modeled with the use of the finite element method (FEM), then calculated with the use of an analytical approach and the results of the two approaches are finally compared. The results of this study show that Helmholtz resonators with multiple resonances at desired frequencies are achievable with the use of additional necks, while FEM and analytical methods can be used for the estimation of the resonance frequencies. Analytical and FEM approach results show a good agreement in cases of small number of additional necks, while the increasing differences in cases of higher neck additions, were attributed to the change in effective length of the necks as demonstrated by FEM. The proposed approach can be useful for tunable sound absorbers for room acoustics applications according to the needs of a space. Also, this approach can be applied in cases of additional tunable air resonances of acoustic instruments (e.g., string instruments). Full article

Broadband noise reduction over the low–mid frequency range in the building and transportation sectors requires compact lightweight sound absorbers of a typical subwavelength size. The use of multi-layered, closely spaced (micro-)perforated membranes or panels, if suitably optimized, contributes to these objectives. However, their elasticity or modal behaviors often impede the final acoustical performance of the partition. The objective of this study is to obtain insights into the vibrational effects induced by elastic limp membranes or panel volumetric modes on the optimized sound absorption properties of acoustic fishnets and functionally graded partitions (FGP). The cost-efficient global optimization of the partitions’ frequency-averaged dissipation is achieved using the simulated annealing optimization method, while vibrational effects are included through an impedance translation method. A critical coupling analysis reveals how the membranes or panel vibrations redistribute the locations of the Hole-Cavity resonances, as well as their cross-coupling with the panels’ first volumetric mode. It is found that elastic limp micro-perforated membranes broaden the pass-band of acoustic fishnets, while smoothing out the dissipation ripples over the FGP optimization bandwidth. Moreover, the resonance frequency of the first panels mode sets an upper limit to the broadband optimization of FGPs, up to which a high dissipation, high absorption, and low transmission can be achieved. Full article

This study aims to analyze the physical-mechanical properties and dynamic models of tissue-simulating hydrogels, specifically the photoacoustic (PA) response signals, by varying the concentrations of polyvinyl alcohol (PVA) and molecular weight (MW). A state-space model (SSM) is proposed to study the PVA hydrogels to retrieve the PA-related signal’s damping ratio and natural frequency. Nine box-shaped PVA hydrogels containing saline solution were used, with five concentrations of PVA (7, 9, 12, 15, 20%) for MW1 and four for MW2. The results indicated that the concentration of PVA and MW played an important role in the PA wave’s amplitude, arrival time, and speed of sound over the hydrogels. The SSM parameters showed that increasing PVA and MW concentrations improved the hydrogels’ ability to absorb and transfer energy under the PA effect. These parameters were also found to be correlated with density and modulus of elasticity. Additionally, the concentrations of PVA and MW affected the absorption and optical scattering coefficients. The physical-mechanical properties, including porosity, density, and modulus of elasticity, improved as the concentration of PVA and MW increased. The ultimate goal of this study is to develop hydrogels as phantoms that can be used for tissue simulation and imaging. Full article