Perforated Panel Research Articles

Application of Hybrid Absorptive–Diffusive Panels with Variable Acoustic Characteristics Based on Wooden Overlays Designed Using Third-Degree-of-Freedom Bezier Curves

This manuscript describes the application of novel hybrid acoustic panels with variable acoustic properties that could be used in the design process. Despite the significant growth in the modern acoustic absorbing and diffusing panel sector in recent years, there is still a need for sustainable and original designs that will fit standard interior design trends. The most significant requirement is satisfying the design needs of variable acoustic venues. The availability of acoustic panels with variable properties is minimal, as most designs are based on textiles in the form of rolling banners; therefore, there is no market diversity. The current paper presents an original solution for a novel perforated wooden panel based on third-degree-of-freedom curves. Due to the possibility of exchanging the front panel, the acoustic surface can be varied and adjusted to the room considering different requirements for the acoustic climate, for example, by modifying the attenuation range from low to mid–high frequencies. The novel panels have unique esthetic properties with functional acoustic features regarding sound diffusion and absorption. In this paper, sound absorption and diffusion measurements will be presented for the different variants of the panels, presenting the option to modify the parameters to adjust the panel’s features to the room’s needs. In situ acoustic measurements in a laboratory were conducted to test the variable acoustic panels’ influence on the room’s acoustic parameters, such as T30 and C80. In summary, the advantages of this kind of design will be discussed, alongside the possible impact on modern construction materials’ utilization in architecture.

A new personalized environment control system for hospital beds with design optimization by Taguchi-based grey relational analysis

The current ward environments consume excessive energy and fail to meet the personal comfort and health needs of patients. A promising solution is to create a personalized bed micro-environment and then extend the ward set-point temperature range. However, there is currently no suitable bed environment control system. This study proposes a novel bedside integrated system with three perforated panels that supplies conditioned air from different directions and prevents direct airflow towards the patient's head region. The system design was optimized using Taguchi-based grey relational analysis (GRA), with predicted mean vote (PMV), draft risk (DR), and personal exposure effectiveness (PEE) considered as response variables. The design variables included supply air temperature, airflow rate, and supply air angles. Taguchi's L16 (44) orthogonal array was employed for the experimental design. The results demonstrate that a low-velocity cold air lake can form above the bed, with the maximum velocity near the patient's head at only 0.2 m/s. In a 28 °C ward, the PMV, maximum DR, and PEE at the bed micro-environment are 0.13, 14.1 %, and 0.67, respectively. This implies that the proposed bed environment control system has the potential to provide both comfort and health benefits while reducing energy consumption. After optimization, the optimal supply air temperature, airflow rate, angles of top panel and side panels are 22 °C, 25 L/s, 0° and 45°, respectively, with an improvement of 5.8 % in the grey relational grade. This study provides a new solution for creating a comfortable and healthy ward environment in an energy-efficient manner.

A study on a micro perforated panel applied luggage board design for road noise reduction

The automotive industry is on the age of rapid transformation from internal combustion engine vehicles to electric vehicles powered by motors. The main source of noise in conventional internal combustion engine vehicles is the engine, while electric vehicles are mainly affected by road and wind noise. A road noise in the medium and low frequency bands, caused by friction between tires and road surfaces, can be improved by increasing the thickness and weight of the insulation material. Still, this countermeasure causes other challenges that related to driving efficiency decrease because of limitations space and weight. As a new method to reduce road noise, therefore, the study introduces the luggage board which applied the micro-perforated panel system. This system utilizes a resonance-type sound absorbing material with excellent sound absorption characteristics at specific frequencies so that a tire pattern noise within the 800-1,000 Hz could be reduced. Because the thickness of the luggage board is partially limited, the study set a number of variations such as changing the porosity, perforated diameter in the perforated panel system. As a result, the study confirmed 2% improvement A.I. (Articulation Index) in the interior with installation of the designed luggage board on the vehicle.

Acoustic metamaterials of double-layer structure for sound insulation

Insulation against air-borne sound is one of the earliest research fields of acoustic metamaterials. The sound insulation of the conventional sound insulation structure is generally limited by the law of mass. When the density of the structural surface is doubled, the low-frequency sound insulation is only increased by 6dB.In our report, we introduce a double-layer resonator-type acoustic metamaterial, which consists of two honeycomb sandwich panels, two perforated panels, and a thin air layer. Firstly, for two singer -layer resonator-type acoustic metamaterial, different sound absorption frequency points were designed. Secondly, a calculation model of sound insulation metamaterial with double-layer resonator type is established. The results show that the sound insulation performance of the structure greatly breaks through the law of mass in the frequency range of 165Hz-3150Hz. Finally, for the application requirements of the manufacturer, the compartment wall components and composite sound insulation door core components are designed. The reasonable design of Double-layer resonator-based honeycomb metamaterial structural parameters can solve the problem of low-frequency noise of thin-layer lightweight structure.

Investigation on enhancement of noise reduction of partially open windows and balconies through mock-up test

Application of Acoustic Windows and Acoustic Balconies is a recent trend in Hong Kong to mitigate road traffic noise impact. In severe situations, enhancement is needed for the mitigation measures to provide additional improvement in acoustic performance. The performances of several common enhancements including micro-perforated absorber panels, perforated absorption panels, and balcony sidewalls are investigated through 1:1 mock-up test. The mock-up test aimed to mimic the actual situation, by referencing the spatial relationship between line sources and receivers. International standards are followed in the mock-up test, including ISO 16283-3: 2016 for microphone setting-out and BS EN 1793-3 for normalized traffic noise spectrum. Based on the mock-up test results, the research revealed that the enhancements' performance changes with line source orientation and suggested the optimum usage of enhancements.

Revisiting the sound absorption mechanisms of a finite flexible perforated panel absorber using a numerical approach.

This study investigates the sound absorption mechanisms of a finite flexible perforated panel absorber. Different from existing work where the mechanisms were often investigated by comparing the sound absorption coefficient curves of different absorber configurations, a numerical approach, called virtual impedance tube (VIT) technique, is developed and used for the analysis. One advantage of this technique is the vast dataset generated can be used to investigate the sound absorption mechanisms from an energy standpoint. The developed VIT technique is first validated using the impedance tube test, where a proportion-integration-differentiation control algorithm is developed to maintain the incident sound at a desired sound pressure level. Then, the sound absorption mechanisms at three absorption peaks, i.e., hole-cavity controlled, panel-cavity controlled, and panel controlled, are investigated and the dominant energy dissipation mechanism at different sound pressure levels (SPLs) is revealed. Finally, an impedance model that takes account of the panel vibration and is applicable to various SPLs is proposed and validated.

Acoustic measurement of super-small-particle-filtering stainless steel wire cloths

The super-small-particle-filtering stainless steel (SSPFSS) wire cloth can serve as a front cover on resonators in mufflers, offering a broader noise reduction bandwidth compared to the resonators themselves. Like micro-perforated panels (MPPs), the SSPFSS wire cloth provides flexibility in resonator design and manufacturing. In this study, we conduct measurements of the transfer impedance of SSPFSS cloths and sound absorption coefficients of absorbers covered by SSPFSS cloths. For comparison purposes, we also calculate the sound absorption coefficient of foam and various absorbers covered by MPPs, traditional perforated panels, and fabric using referenced empirical equations.

In situ acoustic characterization of a perforated panel on a cavity by means of PU measurement and model fitting

The in situ characterization of materials is a crucial challenge in room acoustics, as laboratories measurement cannot always be applied in consultancy practices. In particular, there is a lack of method to characterize in situ systems with perforated facings, which are commonly encountered systems in room acoustics. In this paper, the in situ characterization of a rigidly-backed porous material behind a rigid perforated facing by means of pressure–velocity measurements is presented. The method includes an inverse impedance model fitting based on measurement in a limited frequency range. The applicability of this method was studied by measuring a variety of perforated facings, whether in front of an air cavity or backed by a porous layer, and comparing the obtained impedance model parameters to reference values. Good agreement was observed between the retrieved parameters and the references, with the errors in all retrieved parameters moving mass, facing thickness, cavity depth, porous layer thickness and porous layer flow resistivity not exceeding 15%.

Acoustic measurement of super-small-particle-filtering stainless steel wire cloths

The super-small-particle-filtering stainless steel (SSPFSS) wire cloth can serve as a front cover on resonators in mufflers, offering a broader noise reduction bandwidth compared to the resonators themselves. Like micro perforated panels (MPP), the SSPFSS wire cloth provides flexibility in resonator design and manufacturing. In this study, we conduct measurements of the transfer impedance of SSPFSS cloths and sound absorption coefficients of absorbers covered by SSPFSS cloths. For comparison purposes, we also calculate the sound absorption coefficient of foam and various absorbers covered by MPP, traditional perforated panels, and fabric using referenced empirical equations.

Ghouls Begone: Acoustics of Shrieking Perforated Panels

Under windy conditions, vortex shedding can cause perforated metal skins to emit undesirable noise. This phenomenon was observed, measured, and replicated for different panel sizes and perforation patterns. The acoustical spectrum was analyzed and compared to the modes of a vibrating plate. This study describes the process used to investigate and solve this noise control problem.

Opportunities to use textile waste for the production of acoustic panels

There are many indoor and outdoor areas where one encounters acoustic discomfort. In this study, the design possibilities of a passive acoustic panel with macro-openings are investigated. An acoustic panel which absorbs a defined frequency of sound can be created when a suitable combination of acoustic absorption affecting parameters is found. These optimum parameters for a panel with macro holes were sought by means of experimental research regarding: the type of raw material suitable for the production of the components of the acoustic panel, the optimal hole shapes, their size and positioning on the panel lid, the possibility of using shredded textile from unsorted textile waste. The experiments in which the influence of the hole size and placement on the acoustic absorption was investigated were verified using a theoretical electrical equivalent circuit model created in the MathCad programming environment. The study found that the commonly used perforated panels made of Plexiglas can be fully replaced by panels made of shredded unsorted textile waste. It has also been shown that the shapes of the holes which can act as a design element can have various combinations, i.e. as long as the same percentage of perforation is maintained, the size of the circular holes or the shape of the slotted holes do not matter, as their acoustic absorption is within approximately the same range. The findings published in the study can help in the design of passive panels for both interiors and exterior use.

A simplified homogeneous approach for non-linear analysis of masonry infill panels under in-plane loads

This paper aims to create a unified model that effectively combines continuous 2-dimensional elements and discrete components to capture the nonlinear characteristics and failure mechanisms of solid and perforated masonry infill panels. Given that masonry infill behavior is primarily influenced by shear deformations, an equivalent model is developed by using multiple small square panels arranged diagonally and interconnected by two-component springs, encompassing axial and shear behavior at their intersections. For the sake of simplicity, the divided panels are assumed to behave elastically, with plasticity concentrated only in the axial component of the connector springs. Plastic behavior in the boundary elements was considered to involve both flexural and shear plastic hinges to provide an accurate estimation of the entire infill panel's behavior. To validate this approach, the simplified model is benchmarked against eight experimental masonry infill panels surrounded by steel or reinforced concrete frames and with or without openings. The results including global behavior and crack pattern were compared with available numerical predictions based on finite element method from the literature in addition to experimental outcomes. Ultimately, this comparison demonstrated that the homogeneous model could effectively predict the non-linear lateral behavior of the panels and accurately forecast crack patterns. Additionally, the use of unidirectional non-linear springs and the appropriate arrangement of elastic panels significantly reduced both pre-processing and analysis time.

Investigation into the sound absorptivity of perforated panels with tapered hole geometries coupled with polyurethane foam

Investigation into the sound absorptivity of perforated panels with tapered hole geometries coupled with polyurethane foam

An innovative drying method for on-site and precast walls – Efficiency in accelerating the drying of reduced-scale earth-lime-hemp composites

The drying of construction materials is a challenge regarding structure’s durability and costly construction delays. Long drying periods induce high-moisture content that leads to fungal growth risks. This study presents the development of an innovative forced convection drying method, inspired by unglazed transpired solar wall system and repurposed here for its drying potential at the wall scale. This method employs a metal perforated panel placed at a short distance from the material to dry. This creates an air cavity between them where forced convection is applied with ambient air penetrating through the perforated panel. The moistened air is evacuated thanks to an air circuit composed of a fan and an extraction duct. Two panel configurations with round and cross-shaped perforations are investigated and compared to a natural convection reference. The efficiency of the method is evaluated on Earth-Lime-Hemp composites. With forced convection method, the evaporation front moves moisture towards the near wall forced convection surface and leads to more efficient moisture removal. The results demonstrate a 50 % reduction in drying time using forced convection drying compared to natural convection drying in an open area. Both panel configurations show similar efficiency. The proposed drying method meets the challenges above-mentioned and is applicable for both prefabricated elements and on-site construction. Additionally, it can be effective for the restoration after water damage, enhancing overall construction resilience.

Impact of structural parameters on the acoustic performance of 3D-printed perforated panels combined with polyurethane foam

Impact of structural parameters on the acoustic performance of 3D-printed perforated panels combined with polyurethane foam

Experimental evaluation on compression-after-impact behavior of perforated sandwich panel comprised of foam core and glass fiber reinforced epoxy hybrid facesheets

Abstract To study the impact response and compression-after-impact (CAI) behavior of perforated sandwich panels comprised of foam core and glass fiber-reinforced epoxy hybrid facesheets, the hole diameter of specimens is changed in the fabrication via vacuum-assisted resin infusion. Furthermore, low-velocity-impact tests with various impact distances between the impact point and hole are carried out. With the help of the digital image correlation technique, CAI testing is conducted, and the strain evolution of specimens is monitored carefully. The mechanical response history, damage morphology, and compressive process are discussed in detail. The results show that the impact and CAI performance of specimens are weakened because of open holes. Compared with the non-perforated specimen, the maximum force of the specimen with a 6-mm hole and the 5-mm impact distance decreases by 41.21%, and its maximum displacement increases by 38.60%. During the CAI process, in comparison with the impact damage, more significant stress concentration and buckling around the hole are found.

The sound absorption properties of a double-leaf micro perforated panel (DL-MPP) made from a double-layered polypropylene material.

Micro-perforated panel sound absorbers are recognized as an alternative method for noise control, offering advantages over conventional porous absorbers. However, the sound absorption of a single micro-perforated panel (MPP) is limited in its ability to cover a broad range of frequencies, especially in the low-frequency region. Therefore, the primary focus of this study is to investigate the sound absorption performance of a double-leaf micro-perforated panel (DL-MPP) absorber, which aims to achieve high sound absorption across a wide frequency range. This study examines the impact of varying parameters, including perforation ratio, diameter of perforated holes, and air gap thickness, on the sound absorption characteristics of a polypropylene-based DL-MPP absorber. Polypropylene was used as the sound absorption material for this investigation. The DL-MPP absorber consists of two perforated panels installed parallel to a rigid back wall, with an air gap between them. To assess the sound absorption performance, a prototype of the DL-MPP absorber was fabricated and tested using a two-microphone impedance tube method following ASTM E1050 standard. The results demonstrate that the optimal sound absorption performance was achieved by designing the MPPs with a 1% perforation ratio, 1 mm diameter of perforated holes, and a 1 mm sample thickness.

Sound Absorption of Microperforated Panel Made from Polylactic Acid (PLA)

The microperforated panel (MPP) is a unique panel that has evolved from the traditional perforated panel. Previously, the perforated panel was mainly used as a protective cover for porous materials. The MPP absorbs sound through the viscous effect around its perforated holes. However, traditional MPPs are typically made from metallic materials that are not environmentally friendly. In contrast, polylactic acid (PLA) is a biopolymer extracted from natural resources such as corn and sugarcane. When buried in soil, PLA degrades naturally with the assistance of soil bacteria and fungi, making it an eco-friendly choice. In this study, 3D printing method was utilized to produce MPP using PLA as the material. The sound absorption performance of PLA MPP was compared to steel MPP, which served as the benchmark. Interestingly, the sound absorption performance of PLA MPP was found to be comparable to that of steel MPP. This highlights PLA as a viable material for MPP production, aligning with the global goal of environmental preservation and Sustainable Development Goal (SDG) 12, which emphasizes responsible consumption and production.

Investigation on acoustic performance of distributed periodic micro perforated panel

In this article, an equivalent “material,” called distributed periodic microperforated panel (DSPMPP), is proposed, which is formed by periodically arranging microperforated panels (MPPs). To determine a cubic DSPMPP, 4 parameters are needed, which are size of unit cell L, MPP thickness th, holediameterd and perforation ratio sigma. It is found that d, th, and sL are 3 independent parameters to determine its acoustic properties. Through a homogenization process, DSPMPP is treated as an equivalent material with equivalent density rhoc, speed of sound cc, characteristic impedance zc and bulk modulus kappac, whose frequency dependency is similar to porous material. Acoustic performance of DSPMPP is analyzed, and compared with porous material. It is found that, choosing parameters with the provided procedure, DSPMPP can generally reproduce acoustic performance of porous material.

Acoustic properties of natural fiber reinforced composite micro-perforated panel designed 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 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 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.