Perforated Panel Research Articles

Tunable acoustic metamaterial for broadband low-frequency sound absorption by continuous acoustic impedance manipulation

In this paper, a continuously tunable acoustic metamaterial is proposed for broadband low-frequency sound absorption. The metamaterial can be considered as a reconfigurable Helmholtz resonator with an upper perforated panel that can be continuously rotated to adjust the neck length. A theoretical model is developed to study the tunable sound absorption performance of the metamaterial, which demonstrates that it exhibits efficient low-frequency sound absorption ([Formula: see text]) in the frequency range (from 186 Hz to 319 Hz). Furthermore, perfect sound absorption ([Formula: see text]) is achieved at 197 Hz with a deep subwavelength thickness ([Formula: see text]). To validate this model, numerical simulations and experimental measurements are performed, and the physical mechanism of tunable sound absorption is explored. Results show that the acoustic impedance manipulation is realized by rotating the perforated panel to tune the acoustic mass of the Helmholtz resonator, which is the key to the continuous tunability of the proposed metamaterial. Based on the continuous tunability of each metamaterial unit, a tunable broadband sound absorber is designed to achieve a variety of broadband sound absorption performance with a single fabricated structure. This work paves the way for the manual realization of flexible tunability of sound absorbers and helps to achieve tunable absorption of complex noise according to variable acoustic application scenarios.

Modular by necessity – Bracklinn Falls footbridge

Bracklinn Falls is situated in a gorge surrounded by ancient woodland within the Loch Lomond and the Trossachs National Park. The park authority required a replacement footbridge to cross the gorge and to provide views of the falls. However, access for construction plant and materials was extremely difficult, with the sole access by way of a steep and sharp-cornered path. The construction and access constraints drove the development of a new modular system and governed the structural and aesthetic design for the new footbridge. The resulting structure consists of perforated panels, formed from single sheets of weathering steel folded into a z-shape. These panels were bolted to cross-frames and assembled to create a half-through beam that spans 21.4 m. The scheme achieved an A+ rating under the ‘structural carbon for bridges’ (SCORBs) system (Archer and Green, 2021). The structure was assembled bay by bay and push launched along a set of temporary rails, then jacked onto the permanent bearings. By using a folding process, the modular system minimised welding and hence fabrication time. The system is in the process of being developed for repeated use at other locations, and forms an attractive ‘flat-packed’ modular alternative for difficult to access locations.

Effect of stacking order on the properties of hybrid palm sheath/polyester fiber felt‐reinforced polymer composite laminates

AbstractNatural fiber‐reinforced composites exhibit excellent mechanical properties. However, achieving a balance between excellent mechanical properties and optimal acoustic performance remains a challenge. In this study, four composite laminates with different stacking orders were fabricated using polyester fiber mats (WFs) and palm sheaths (WPs) through a hot‐press process. Moreover, the effects of different stacking orders on the mechanical and acoustic properties of the composite were investigated. The results revealed that the incorporation of polyester fiber felts and the modification of the layup sequence of WP and polyester fiber felts significantly improved the mechanical and acoustic properties of the composites. Scanning electron microscopy images revealed a strong bonding between palm fibers and polyester fibers at the epoxy resin interface. Compared with pure palm fiber composites, the alternately stacked palm fibers and polyester fibers (WP/WP/WF/WP/WF) exhibited the highest mechanical properties, with a significant enhancement of 142.67% and 16.90% in flexural and tensile strengths, respectively. Additionally, the peak absorption coefficient of polyester fiber felts, positioned in the surface layer of the composite material, within the 2580–3400 Hz frequency band significantly increased from 0.07 to 0.44. Therefore, this study indicates that modifying the stacking order improves the mechanical and acoustic properties of the composites, making them suitable for use in acoustic engineering materials for buildings and decorative panels for furniture, including perforated panels and acoustic screens.Highlights The fabric‐like textured structure significantly enhanced the overall performance of the composites. The stacking order significantly influenced the overall properties of the composite. Alternately stacked polyester fiber felts and palm fibers exhibited excellent mechanical performance. The polyester fiber felts positioned on the surface layer of the composites exhibited superior mechanical performance. A laminate with “green” attributes and good acoustic properties was fabricated.

Acoustic properties of natural fiber reinforced composite micro-perforated panel (NFRC-MPP) made from cork fiber and polylactic acid (PLA) using 3D printing

The present study investigated the acoustic performance of biodegradable MPP absorbers made of natural fiber-reinforced composites (NFRC) using 3D printing. The novelty of this current research lies in the recent development of a methodology that aids industry professionals in optimizing the production of MPP (Micro-Perforated Panel) at a competitive cost. This is achieved by addressing and eliminating various issues commonly faced in traditional manufacturing processes, such as manual preparation and pressing. The FDM technique was used to fabricate test samples utilizing the PLA/corkwood composite. Using an impedance tube device with two microphones, the acoustic absorption coefficients of MPPs with different perforation diameters, thicknesses, and perforation rates were measured. Maa's analytical model was used to predict the acoustic absorption performance. Moreover, considering the average sound absorption and total cost of fabricating the samples, RSM-CCD was employed to optimize these samples. In the end, the parallel arrangement of MPP double layer and the combination of MPP with kenaf porous material were tested in order to improve the sound absorption performance. The results showed that the average sound absorption coefficient of the NFRC-MPP sound absorber is 25 % more than that of conventional MPP sound absorbers. The sample with a perforation diameter of 0.70 mm, a panel thickness of 0.90 mm, and an 8 mm distance between the perforations was selected as the optimal sound absorber. The measurement and model data for NFRC-MPP panels do not correspond well. The parallel arrangement of two layers of MPP and the addition of an optimized kenaf layer behind the MPP significantly improved the sound absorption performance in the intended frequency range. The findings of this study, coupled with data available in the literature for other types of biocomposite Micro-Perforated Panel (MPP), strongly indicate that Cork fiber-based MPP exhibits substantial promise for application, either independently or in conjunction with Kenaf materials, as a material for acoustic conditioning. Implementing smart manufacturing techniques for acoustic panels not only enhances engineering noise control efforts but also amplifies the overall effectiveness of Hearing Conservation Programs.

A multi-strut model for the hysteresis behavior and strength assessment of masonry-infilled steel frames with openings under in-plane lateral loading

The analysis of masonry-infilled frames (MIFs) with openings is a complex problem in structural engineering. Previous studies have shown that when an infill panel has an opening, it behaves as four separate subpanels around the opening. Therefore, it can be conceived that a perforated masonry infill panel behaves as four inclined compression-only equivalent struts in each direction. This paper presents a multi-strut model (MSM) using the equivalent strut concept for the nonlinear analysis of masonry-infilled steel frames (MISFs) with openings. The MSM consists of two inelastic side pier struts connected to the surrounding frame joints using rigid trusses representing the subpanels above and below the opening. The model incorporates an envelope curve and a hysteretic law to define the initial stiffness, peak strength, and post-peak strength behavior of the inclined struts under reversal loads. The MSM was used to analyze the lateral load behavior of tested MISFs with openings found in the literature. It was shown that the proposed model is efficient and can predict the stiffness and capacity of MISFs with openings under both monotonic and cyclic lateral loadings.

Sound absorption of acoustic resonant absorbers with rough oblique perforations

Micro-perforated panel sound absorbers are widely used in the field of noise reduction due to their good sound absorption performance. For micro-perforated panel, the acoustic impedance characteristics of the perforation hole play an extremely important role in the sound absorption performance. Here, the acoustic metamaterial in the form of a perforated panel with rough oblique holes is proposed for low-frequency sound absorption. By introducing surface roughness, the acoustic performance of the oblique perforation holes can be adjusted, and the low-frequency sound absorption performance of the perforated panel sound absorber is improved. The theoretical prediction of sound performance has been verified by finite element simulation, and a good consistency has been achieved. The results show that the introduction of surface roughness effectively reduces the resonant frequency and increases the value of sound absorption peak. The introduction of surface roughness and oblique configuration can provide additional acoustic resistance and reactance for impedance matching with air without increasing the thickness of the structure, resulting in more effective low-frequency sound absorption. Physically, the surface roughness causes the periodic concentration effect of the fluid vibration in the hole, which increases the viscosity loss and improves the sound absorption performance of the sound absorber. The theoretical and the numerical models, as well as the low-frequency perfect sound absorption performance (α>0.99) of the proposed metamaterial, are validated by experimental measurements. This work is of great significance to the application of perforated panel absorbers in low-frequency sound absorption.

Sound absorption of resonators or perforated panels with multiple folded long tubes crammed in small module by additive manufacturing

Resonators or perforated panels give a large sound absorption at a resonant frequency tuned by opening area of the pores, neck length and a cavity depth behind the neck. The author has studied the sound absorption of thin tile-like resonators tuned at low frequencies by including a folded long neck in its surface panel. The resonators are made by an additive manufacturing with a fused deposition modeling (FDM). This paper makes the resonators or the perforated panels with multiple folded long tubes and discusses its measured sound absorption characteristics. One of the multiple folded long tubes is crammed in 12 mm × 12 mm × 19.2 mm of rectangular module even if the tube has 2 mm × 2 mm of opening area and 288 mm of length. A perforated panel consisted of planar periodic arrays of this module gives a large sound absorption at 69 Hz when a 40 mm depth of cavity behind the perforated panel. Furthermore, when the planar periodic arrays of small Helmholtz resonators applied single module and single cavity tuned at different resonant frequency, it has potential to form an acoustic metasurface with sound absorption at broadband frequencies.

Optimal design for a perforated panel absorber combined with Helmholtz-resonance and plate vibration

This study proposes a perforated panel sound absorber combined with Helmholtz-resonance and plate vibration and its optimal design method to broaden the sound absorption characteristics. The proposed perforated absorber has a simple structure consisting of a flexible panel with a hole and an air cavity. The conventional optimal design theory of the dynamic vibration absorber is applied to the perforated absorber. The proposed absorber is designed so that the acoustic impedance density will be equalized and almost minimized at two points independently of the damping of the panel. Optimal parameters are related to the Helmholtz-resonance frequency, the natural frequency of the panel, and the loss factor of the panel. The absorber with the optimal parameters was fabricated, and the sound absorption coefficient was measured using an acoustic impedance tube. The experimental results shows that the proposed method can effectively design the perforated panel absorber with the broadband sound absorption characteristics.

Sound absorption performance analysis of perforated panel resonator with tube bundles based on independent adjustment impedance

A method of independent adjustment of acoustic resistance and acoustic reactance is proposed for the problem of coupling of acoustic resistance and acoustic resistance affecting impedance matching in sound resonant absorbers. Combining theoretical analysis model and finite element simulation model, the modulation mechanism of independent adjustment impedance is revealed. Theoretical and simulation results show that for the same structural thickness and perforation rate, the acoustic resistance of the perforated panel resonator with tube bundles (PPTB) varies with the inner diameter of the tube, but the acoustic resistance remains constant. The PPTB can exhibit different damping states at the same resonant frequency and show different sound absorption performances. The experiment verifies that independent adjustment impedance can improve the impedance matching effect and enhance the sound absorption performance. In addition, the influence of structural parameters on the sound impedance is discussed. Moreover, independent adjustment impedance can be expected to design low-frequency broadband sound absorption structures and optimize sound absorption bandwidth.

Analysis of nonlinear landscape structure components accurate construction information delivery based on Rhino+Grasshopper parametric modeling

The development of digital construction technology has made the practical construction of nonlinear forms possible. In landscape architecture projects, Nonlinear Landscape Structures (NLS) have become the mainstream in design and aesthetics. However, the complex forms of NLS components make it challenging to deliver accurate construction information using traditional design methods. The application of Rhino+Grasshopper Parametric Modeling (RGPM) technology allows the construction of nonlinear geometric forms based on mathematical logic, facilitating precise engineering construction information delivery for NLS components. Nevertheless, there are existing gaps in current research on accurate construction information delivery for NLS components based on RGPM. Firstly, current research primarily focuses on large public buildings, lacking attention to the spatial scale of landscape structures. Secondly, there is a lack of systematic integration based on technical research contents. Thirdly, there is a lack of specific technical application analysis combining actual design, leading to weaker practical guidance for industry practitioners. Therefore, this study selects the precise engineering construction information delivery of perforated panel walls in the space under the Sanya Bridge and the landscape platform of the Beijing Jinding Mountain as research cases. Through the analysis of construction information delivery content and technical challenges in these cases, the necessity of RGPM application is clarified. By analyzing the application of RGPM technology and its outcomes in these cases, concrete examples are provided for the precise construction information delivery of NLS components to fill the research gaps and provide theoretical foundations and application examples for future research.

Analysis of nonlinear landscape structure components accurate construction information delivery based on Rhino+Grasshopper parametric modeling

The development of digital construction technology has made the practical construction of nonlinear forms possible. In landscape architecture projects, Nonlinear Landscape Structures (NLS) have become the mainstream in design and aesthetics. However, the complex forms of NLS components make it challenging to deliver accurate construction information using traditional design methods. The application of Rhino+Grasshopper Parametric Modeling (RGPM) technology allows the construction of nonlinear geometric forms based on mathematical logic, facilitating precise engineering construction information delivery for NLS components. Nevertheless, there are existing gaps in current research on accurate construction information delivery for NLS components based on RGPM. Firstly, current research primarily focuses on large public buildings, lacking attention to the spatial scale of landscape structures. Secondly, there is a lack of systematic integration based on technical research contents. Thirdly, there is a lack of specific technical application analysis combining actual design, leading to weaker practical guidance for industry practitioners. Therefore, this study selects the precise engineering construction information delivery of perforated panel walls in the space under the Sanya Bridge and the landscape platform of the Beijing Jinding Mountain as research cases. Through the analysis of construction information delivery content and technical challenges in these cases, the necessity of RGPM application is clarified. By analyzing the application of RGPM technology and its outcomes in these cases, concrete examples are provided for the precise construction information delivery of NLS components to fill the research gaps and provide theoretical foundations and application examples for future research.

Broadband sound absorption based on impedance decoupling and modulation mechanisms.

In sound absorbers, acoustic resistance and reactance are usually coupled together and affect each other, which brings difficulties to impedance matching. An impedance decoupling method is proposed to make acoustic resistance and acoustic reactance vary independently. For the same thickness and perforation rate, acoustic reactance of the perforated panel with tube bundles (PPTBs) varies with the diameter of the tube, but acoustic resistance remains constant. Theoretical and simulated results show that a PPTB absorptive unit can exhibit resonance modes with varying damping states through impedance decoupling. It is found that through well-modulation, the PPTB unit in a slightly over-damped state cannot only maintain high sound absorption coefficients, but also expand the absorption peak bandwidth. Utilizing the mechanism of impedance decoupling, a broadband absorber is designed and evaluated by comprising the PPTB and microperforated panel (MPP). Measurement results indicate that it possesses an average absorption coefficient of 85% spanning more than a 3-octave bandwidth from 160 Hz to 1400 Hz with a deep sub-wavelength thickness. The impedance decoupling method helps to implement sound absorbers with highly efficient low-frequency broadband absorption.

Hysteresis behavior of Auxetic Perforated Steel Plate Shear Walls with elliptical and peanut-shaped cutouts

Although auxetic (negative Poisson’s ratio) materials and structures have unique mechanical properties, their application in earthquake-resistant structures is rarely reported. This paper proposed a novel Auxetic Perforated Steel Plate Shear Wall (AP-SPSW) for seismic mitigation in building structures. The AP-SPSW incorporates the unique mechanical properties of auxetic materials and structures to reduce out-of-plane buckling and improve seismic performance of SPSWs. Both elliptical and peanut-shaped perforation configurations were proposed for the AP-SPSW. Through small-scale numerical simulations of the auxetic unit cells, the deformation mode of the auxetic perforated material was discussed and a preliminary design was presented to ensure the materials with negative Poisson’s ratio. In addition, ten AP-SPSW specimens were prepared for cyclic loading tests, which demonstrated that the AP-SPSW possesses stable hysteresis behavior and excellent energy dissipation capacity. Key parameters affecting the hysteresis performance of the AP-SPSW were identified as porosity of the perforated panel and thickness of the ligament between neighboring perforations. This study also focused on the global shear buckling behavior of the auxetic perforated panel plates. It was found that the auxetic deformation mechanism benefits shear buckling resistance in the SPSW panel. Finally, an analytical model was proposed for the shear strength of the auxetic panel. The limitations of this study were also discussed, along with the work required for further exploration. The results of this study provide valuable insights for the development of innovative seismic-resistant structures that incorporate auxetic materials and structures.

Low-frequency broadband absorber with coherent coupling based on perforated panel and space-coiling channels

Efficient broadband absorption of low-frequency sound via ultra-thin structure remains challenging due to the narrow-band property generated by the dispersive nature of resonance. In this study, we investigate the absorption mechanism of a component composed of a perforated panel and space-coiling channels through the coupling effect, acoustic impedance matching, and complex frequency analysis. In addition, the influence of geometrical parameters, resonance frequency intervals, and number of components in the coupled system on the band is investigated. Accordingly, the strategy for developing absorbers is to design individual components in the under-damped state by adjusting the geometrical parameters, then put together multiple components with different channel lengths in parallel. On the basis of this strategy, a low-frequency and broadband absorber is theoretically proposed and experimentally demonstrated, which can achieve broadband absorption from 250 Hz to 450 Hz. The design strategy has potential applications in low-frequency noise control engineering, such as plants, automotive and aerospace industries.

Sustainable Perforated Acoustic Wooden Panels Designed Using Third-Degree-of-Freedom Bezier Curves with Broadband Sound Absorption Coefficients.

The current interior design scope places high demands on acoustic treatment manufacturers. The state of the art does not provide satisfactory material proposals for architects to satisfy design needs. There is a need for a novel approach concerning decorative, recognized materials that adapts them to the acoustic surface properties. The final design proposed in this study presents a modern functional solution with high acoustic properties, which can be produced with sustainable materials such as FSC wood and has a low environmental impact because of its low waste production. This research presents the complete design process of a novel type of wooden acoustic panel. A comprehensive explanation of the scientific development is covered, including basic material testing in an impedance tube, FEM simulations of the initial designs, and final measurements in a reverberation chamber. The solution's novelty is based on the optimized placement of the perforation holes on the surface of a wooden overlay using a ship deck optimization algorithm. The methods used cover the original solution of mixing FEM modeling of the surface impedance with the application of the Jeong-Thomasson correction for random incidence sound absorption coefficient simulation. The contribution of this research is the development of wooden perforated panels with Class A sound absorption and an overall depth of 90 mm, including the 50 mm depth of the backing material. The discussion will explain the difficulties of working with this material and the need for a combination of the aesthetic and acoustic sides of the project.

Sound absorption mechanism of sonic black hole with labyrinthine units and micro perforated panel

Acoustic black hole (ABH) is a technique capable of manipulating the propagation of flexural wave, and the sonic black hole (SBH) is a kind of ABH which is used to manipulate sound wave in a fluid medium. In this paper, we propose an SBH structure with labyrinthine units and combine with micro-perforated panel (MPP) to form a composite sound absorption structure. The sound absorption mechanism of the absorption structure is deeply investigated using numerical and simulation methods. The simulation reveals the sound absorption mechanism by acoustic streaming effects of composite sound absorption structure. We analyze the flow characteristics of the acoustic medium under acoustic excitation, and the effect of the flow field on the distribution of the acoustic field, and the energy dissipation distribution. Our theoretical results show that the sound absorption is attributed to the effects of sound energy focusing of ABH, the local resonance of MPP, and the acoustic energy localization and dissipation effect of labyrinthine units caused by large flow velocity gradients. Finally, the proposed composite sound absorption structure has good sound absorption performance, which is also confirmed by impedance tube experiments. It can provide a new way of thinking for the design and optimization of the SBH structure.

Predicting buckling loads of perforated rectangular isotropic panels using Gene Expression Programming and Artificial Neural Network

This study aims to develop semi-empirical formulas for foretelling the buckling loads of clamped and simply supported rectangular isotropic panels with central circular perforation exposed to different ratios of biaxial load conditions. The empirical formulas were developed and evaluated using Gene Expression Programming (GEP), Artificial Neural Network (ANN), and Finite Element Method (FEM). A total of 714 data set, generated using the FEM, is used to establish and validate the empirical formulas. This study investigates the effect of perforation sizes, plate aspect ratios, and biaxial load ratios on the buckling strength of perforated panels. The proposed formulas will allow a quick and easy estimation of buckling loads for perforated rectangular panels with acceptable accuracy without the need for sophisticated calculations. The results of the empirical formulas were comparable reasonably well with the results of the finite element analysis (FE) and available literature findings.

Investigations on predictions of cooling capacity for open refrigerated display cabinet using CFD approach with different positions of perforated back panels

Investigations on predictions of cooling capacity for open refrigerated display cabinet using CFD approach with different positions of perforated back panels

Numerical analysis of Plastic Perforated Panel for Acoustic Protection

Acoustic protection is an important aspect in various industrial, commercial and residential applications. In order to reduce the transmission of noise, perforated panels are frequently used as a barrier. The present study aims to conduct a numerical analysis of plastic perforated panels for acoustic protection. The study employed a finite element method (FEM) approach and focused on the propagation of acoustic waves through perforations of varying diameters (30 mm, 40 mm, 50 mm, 60 mm, 70 mm and 90 mm) and at different frequencies (250 Hz, 500 Hz, 1000 Hz and 1500 Hz). The numerical analysis was conducted using the finite element software ANSYS. This work offers numerical analysis models of acoustic wave propagation, which can be used by those interested in similar problems, for different environments, in closed or open spaces. The results showed that the perforation diameter and frequency play a crucial role in the performance of the plastic perforated panels as an acoustic barrier. The results of the author�s research pointed out that the plastic materials can be used successfully in the construction of acoustic barriers. Next to it, the findings of this study can provide valuable insights for engineers and designers in the selection and optimization of plastic perforated panels for acoustic protection applications.

Sound absorption coefficient measurement and analysis of bio-composite micro perforated panel (BC-MPP)

Sound absorption coefficient measurement and analysis of bio-composite micro perforated panel (BC-MPP)