Acoustic Panels Research Articles

Acoustic Simulations Applied to the Garden of Rufolo’s Villa in Ravello: Comparison between Different Scenarios

This manuscript treats the acoustic analysis of a garden located in Rufolo’s villa, south of Italy, which has already been studied to install some acoustic panels to improve the response across the seating area. After a campaign of acoustic measurements, acoustic simulations have been conducted based on three specific scenarios, highlighting the effectiveness of a new acoustic shell (project C) over the existing conditions (project A) and option A shell (project B). The results coming from the simulations show that the values of the main acoustic parameters are significantly improved with the installation of a scientifically designed acoustic shell, to be closer to the optimal ranges. The comparison among different projects highlights that the acoustic response of the existing conditions is not optimal, and that a marginal improvement was found with the addition of vertical panels mounted at the perimeter of the stage in combination with suspended ceiling above the stage. This research study is addressed to potentially auralize the voice or sound of famous artists that would be performing within the new acoustic shell; furthermore, the outputs could even implement the website of the Rufolo’s villa for marketing purposes.

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.

Prototyping Industry 4.0: The Case of an Automated Stapler for Acoustic Slat Panel Production

This paper explores the practical adoption challenges of Industry 4.0 principles in Small Enterprises (SEs), particularly through the development of an automated stapler prototype for acoustic slat panel production. The study presents a case where the prototype, costing less than 400 euros, is shown to potentially increase the production rate by 42%, showcasing the feasibility of cost-effective, tailored solutions in digitizing manufacturing processes within SEs. It demonstrates that such incremental improvements can substantially boost productivity and efficiency, enabling SEs to better compete in increasingly demanding markets while also mitigating the high cost and physical strains associated with manual labor. The presented approach of prioritizing significant improvements over complete automation aligns well with the practical and financial constraints of SEs. Moreover, the paper challenges the notion that the adoption of Industry 4.0 necessitates substantial investment, by highlighting the importance of flexible, low-cost prototyping in overcoming financial and technical constraints, suggesting a shift towards accessible digital transformation in the manufacturing sector.

Utilization of Luffa for Acoustic Panel on Interior Wall, A Technical and Perceptual Approach

Luffa Cylindrica is one of Indonesia’s biodiversity, which provides several benefits, such as for making handycraft, cleaning tool and event for building materials. This study aims to investigate the ability of Luffa as a sound absorber and its visual impression when applied to interior walls. The first stage is testing the damping ability of panels made of Luffa. Several specimens of Luffa acoustic panels were made with PVAc adhesive and then tested to determine their damping ability. From the test results using the impedance tube method (ASTME1050-12), the samples met the soundproof requirements with an absorption coefficient of 0.15 - 0.206 at a frequency of 1600 Hz. The lost sound transmission values obtained are in the range of 40-60 dB. Thus, Luffa can be used as a good sound-absorbing material. The next stage is the development of the visual design of the panel so that it has a certain aesthetic or perceptual value. Three designs were made with variations in shape and color into nine samples applied to a wall of interior space. The semantic differential method assessment found that simple and decorative impressions dominated when the panel was applied to interior walls.

Thermal and acoustic characterization of nanofibrous polymeric structures for insulation applications

Nanofibrous structures are engineered materials for high-end applications. The impact of electrospinning settings on the thermal and acoustic properties of polyurethane (PU) nanofibrous structures is examined in this research. The excellent sound-absorbing properties of PU make it a versatile material that may be used in a variety of acoustic applications. The study focuses on how PU nanofiber morphology, such as fiber diameter and volume fraction, is affected by varying ambient conditions. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) are used to examine the stability and thermal behavior of PU nanofibers. The findings show that raising the fiber volume fraction improves thermal stability and changes the way PU nanofibers behave thermally. PU nanofiber webs provide efficient sound absorption in low and intermediate frequency ranges according to the study's analysis of the sound absorption coefficients. According to the results, PU nanofiber webs may offer novel approaches to noise control, especially in situations where acoustic panel insulation is needed with no weight penalty.

Extremely tortuous sound absorbers with labyrinthine channels in non-porous and microporous solid skeletons

An assembly of additively-manufactured modules to form two-dimensional networks of labyrinthine slits results in a sound absorber with extremely high tortuosity and thereby a relatively low-frequency quarter wavelength resonance. Fully analytical modelling is developed for the generic design of such composite acoustic panels, allowing rapid exploration of various specific designs. In addition to labyrinthine channels in a non-porous solid skeleton, a case is also considered where the skeleton has microporosity such that its permeability is very much lower than that due to the labyrinthine channels alone. The analytical modelling is verified by numerical calculations as well as sound absorption measurements performed on several 3D printed samples of modular composite panels. The experimental validation required overcoming the non-trivial difficulties related to additive manufacturing and testing samples of extreme tortuosity. However, due to the two-dimensionality and modularity of the proposed design, such absorbers can possibly be produced without 3D printing by assembling simple, identical modules produced separately. The experimental results fully confirmed the theoretical predictions that significant sound absorption, almost perfect at the peak, can be achieved at relatively low frequencies using very thin panels, especially those with double porosity.

The reduction of the reverberation using the sound-absorbing metamaterial in the conference rooms

Sound-absorbing metamaterial, iwasemi consists of multiple perforated Fabry-Perot resonators which have different resonant frequencies reciprocally to achieve broadband sound absorption coefficient. We have installed acoustic panels that are optimized for the main band of human voices, 1/3 octave band center frequencies from 500 Hz to 1000 Hz, in some conference rooms and measured the reverberation time of the rooms before and after installation. The measurement result shows that the acoustic panels have decreased the reverberation time of the rooms dynamically in the target frequency band (e.g. a case of we measured, the reverberation time reduced from 1.11 seconds to 0.66 seconds at 500 Hz octave band center frequency). As shown above, it has been indicated that installing plastic acoustic panels using acoustic metamaterial improves the acoustic environment in the rooms.

Effect of Small Concaves Surface on the Acoustical Characteristics of Chicken Feather Panel

This study aims to determine the impact of small concave surfaces on the acoustic characteristics of chicken feather panels. Based on the feather-glue ratio reference, the researchers applied a mixture of 70% feather and 30% PVAc for the production of the specimens. In the first stage, the absorption coefficient of the specimen on a small concave surface (CS) was measured using an impedance tube type B&K 4602 with two microphones and a set of computer FFT analyzers. The measurement results were then compared with the absorption coefficient of similar test objects with flat surfaces (FS). The acoustic characteristics of the two types of surfaces (FS and CS) in the specimen panel showed the maximum absorption coefficient (α) value of 0.52 and 0.63 for FS and CS, respectively. These results indicate that specimens with a small concave surface (CS) have a relatively higher absorption coefficient than those with a flat surface (FS). However, further studies are needed to identify other characteristics of these acoustic panels, including their resistance to environmental influences.

Fabric defect detection using AI and machine learning for lean and automated manufacturing of acoustic panels

Fabric defects in the conventional manufacturing of acoustic panels are detected via manual visual inspections, which are prone to problems due to human errors. Implementing an automated fabric inspection system can improve productivity and increase product quality. In this work, advanced machine learning (ML) techniques for fabric defect detection are reviewed, and two deep learning (DL) models are developed using transfer learning based on pre-trained convolutional neural network (CNN) architectures. The dataset used for this work consists of 1800 images with six different classes, made up of one class of fabric in good condition and five classes of fabric defects. The model design process involves pre-processing of the images, modification of the neural network layers, as well as selection and optimisation of the network’s hyperparameters. The average accuracies of the two CNN models developed in this work, which used the GoogLeNet and the ResNet50 architectures, are 89.84% and 95.45%, respectively, showing statistically significant results. The interpretability of the models is discussed using the Grad-CAM technique. Relevant image acquisition hardware requirements are also put forward for integration with the detection software, which can enable successful deployment of the model for the automated fabric inspection.

Increased modal damping of undamped single and multiscale acoustic black hole panels.

The acoustic black hole (ABH) effect has been shown to increase damping of structures by focusing energy into a tapered-thickness region with added damping material. This paper illustrates that enhanced damping can be achieved without the use of damping material. Three panels were designed with different ABH grid patterns and parameters and compared to a baseline panel. Increased damping is shown to exist for two of the three ABH panels even though no damping material was applied. The panel modes which exhibited increased damping were local to the ABH grid while global modes did not exhibit increased damping.

Acoustic wave propagation through eco-friendly porous panels at normal incidence

Human and non-human subjects are exposed to micro plastics through drink, food, and air. Micro-plastics propagating through atmosphere are breathable particles during inhalation and exhalation leading to deposition of them in the deep lung via the alveoli of the lungs. Teabags are made of plastics that are not recyclable and biodegradable. Therefore, we intend to remove used teabags from the natural environment by repurposing them to make sound attenuating panels for building and architectural industries, contributing in this way to a sustainable circular economy. The panels were designed and developed from consumed teabags as porous material by filling a frame to investigate acoustics wave propagation through them at normal incidence. Experimental testing was carried out on circular teabag panels in an impedance tube using a transfer function method to determine their sound absorption coefficient and transmission loss. Furthermore, the impedance gun method was used to determine the absorption properties of square panels. Results show that 75 mm thick circular panels give an absorption coefficient higher than 0.8 between 400 and 1600 Hz. Up-to 9.8 dB sound transmission loss of circular panels is obtained at higher frequencies. Absorption coefficients for square teabag panels are very good despite a coincidence-dip seen at 800 Hz. The satisfactory sound absorption and sound transmission characteristics of acoustic panels made of consumed tea bags can make this recycled material a cost-effective solution in the production of sustainable acoustic treatment in indoor spaces. The results suggest that recycling of consumed teabag as the panel could be applied as alternative sound absorbing materials.

Design Of aesthetic acoustic metamaterials window panel based on Sierpiński triangle for sound-silencing with free airflow

Design of high-efficiency, low frequency (<1000Hz) soundproof window or wall absorber which is transparent to airflow is presented. Due to the massive rise in human population and modernization, environmental noise has significantly risen globally. Prolonged noise exposure can cause severe physiological and psychological symptoms like nausea, headaches, fatigue, and insomnia. There has been continuous growth in building construction and infrastructure like offices, bus stops, and airports due to urban population. Generally, a ventilated window is used for getting fresh air into the room, but at the same time, unwanted noise comes along. Researchers used traditional approaches like noise barrier mats in front of the window or designed the entire window using sound-absorbing materials. However, this solution is not aesthetically pleasing, and at the same time, it is heavy and not adequate for low-frequency noise shielding. To address this challenge, we design a transparent hexagonal panel based on Sierpiński fractal triangle which is aesthetically pleasing, demonstrates normal incident sound absorption coefficient more than 0.96 around 700 Hz and transmission loss around 23 dB, while maintaining air circulation through triangular cutout. Next, we present a concept of fabrication of large acoustic panel for large-scale applications which lead to suppressing the urban noise pollution

Способ уменьшения производственного шума

Despite the presence of numerous organizational and technical methods and means of combating noise in production, as well as acoustic pollution in the field of environmental protection, the issue of reducing industrial noise remains relevant at present. An effective method of reducing noise in technical premises is to line the walls and ceilings with sound-absorbing panels. The use of sound-absorbing panels allows to minimize the effect of reflection of sound waves incident on hard enclosing surfaces, as well as reduce the transfer of sound energy to adjacent rooms or to the surrounding space. The methods of installation of sound-absorbing panels directly affect the acoustic characteristics of the sound-absorbing cladding. Sound absorption is enhanced when acoustic panels are placed at a certain distance from the surface of the enclosing floor. By adjusting the air gap between the back surface of the panel and the wall surface, it is possible to achieve fairly acceptable sound absorption characteristics in the low-frequency sound spectrum. An effective way to improve the acoustic characteristics of panel cladding is to use narrow-gap panel layouts, where the opposing end faces of adjacent panels are located with some air gap. In this case, the principle of diffraction edge effect is used, with sound waves bending around the end sections of the panel and further dissipative dissipation of acoustic energy in a porous sound-absorbing substance. However, the features of the relative position of sound-absorbing panels are not studied in sufficient detail, the dependence of the efficiency of sound absorption on the geometric dimensions of the air gaps between the panels is not assessed, which is the purpose of this study. During this process, the optimal geometric parameters of the relative position of sound-absorbing cladding panels were determined, which make it possible to increase the acoustic properties of the cladding.

ENVIRONMENTALLY FRIENDLY ACOUSTIC PANEL DESIGN FROM CURTAIN WASTE

Using leftover industrial curtain fabrics, this study aims to develop environmentally friendly acoustic panels. In this context, two forms of curtain fabric waste, blackout and dimout, which are segregated as waste from post-production process within Oba Perdesan, are transformed into fiber utilizing mini shredder. The hot press method is used to produce composite samples made of 100% blackout and 50% blackout/ 50% dimout fabric waste in two different thicknesses (0.5 and 1 cm). The thickness, density, basis weight, FTIR, sound absorption coefficient, and sound transmission loss of the manufactured panels are measured. The FTIR analysis reveals the distinctive peaks of the raw materials of the structures, while the acoustic test results show that the sound absorption coefficient and sound transmission loss increase along with the thickness and basis weight of the structures, respectively. While the 1 cm blackout/dimout blend sample has a superior sound absorption coefficient for 2000 Hz with 0.81, the 1 cm 100% blackout sample performs highest with 10dB sound transmission loss. The produced panels aid in solid waste management while consuming minimal raw materials, and an essential step is taken toward the development of sustainable, practical, and decorative panels.

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.

Investigation of structural parameters of acoustic panels produced from post-industrial textile wastes containing different raw materials

Although noise pollution appears to be a minor issue, it worsens as a result of urbanization and population growth. Unwanted noises have a wide range of negative effects, including anxiety, hostility, high blood pressure, tinnitus, hearing loss, and sleep difficulties. The researchers are compelled to conduct a creative search in order to uncover future environmental solutions due to the noise problem, which is becoming each day worse. Moreover, the textile sector, which is growing day by day, generates huge amounts of waste with the effect of fast fashion trend. The objective of this study is to develop ecofriendly acoustic panels utilizing recycled textile waste and thermoplastic polypropylene (PP) fibers. Within the scope of the study, waste fabrics made of viscose, lyocell, flax, cotton, and polyester are shredded into fibers, and sandwich panels including waste fibers bonded together with PP fibers are generated using the hot press technique. In addition to the use of natural and synthetic fibers, the effects of surface shape (perforated-imperforated) and layer thickness (5 mm and 10 mm) on acoustic performance are examined. The results of the sound absorption and sound transmission loss tests reveal that the acoustic properties of the samples improve as the sample thickness increases, but the perforation process does not have the desired favorable impact on samples of the same thickness. Additionally, the outcomes demonstrate that around 2000 Hz, natural and regenerated fibers with high cellulose content had the best sound absorption coefficients around 0.60. The findings indicate that these eco-friendly panels can be used to reduce unwanted noise in open offices, co-working spaces, and meeting rooms.

Achieving acoustic comfort in the library: a sound masking initiative

Purpose The purpose of this paper is to highlight the sources of noise generation in a library and suggest the implementation of a sound masking system to provide acoustic comfort, maintain speech privacy and create an environment more engaging for the users. Design/methodology/approach Analyzing the existing literature and exploring the existing practices as observed in different libraries, the study gives an overview of the sound masking initiatives in libraries. Findings With practical examples of libraries, the study demonstrates how a sound masking system has been implemented to invoke better acoustic design in the library. The expansion of various activities in the library and a gradual shift from individual attention to a collaborative approach necessitates a strong focus on the acoustic design architecture of the library. The study showcases how the libraries adopt sound masking with the introduction of acoustic panels, dual panel partitions, sound-absorbent false ceilings, sound insulation, sound isolation and noise-dampening measures, installing furniture with sound containment features, adopting vibration control mechanism, mounting of white noise machines, etc., keeping the aesthetic quotient of the library alive. Originality/value The study attempts to show the current practices of the adoption of the sound masking system in libraries and promotes collaborative reading with the creation of an acoustic design-influenced library environment to control noise and reverberation and provide a comfortable reading environment.

Valorization of Moroccan Hemp Waste: Study of the Possibility of its Use in Thermal and Acoustical Insulation of Buildings

This paper aims to study the possibility of valorizing hemp residues in order to develop new local bio-composites from Moroccan hemp shiv and epoxy. The goal is to use them as thermal and acoustical insulation panels since these hemp residues exist in large quantities in landfills and present a national concern due to a lack of waste management technologies. For this purpose, several samples were prepared for different densities and two sizes of hemp shiv; crushed shiv (CS) and fibred shiv (FS). The results revealed that the increase of density resulted in an increase in thermal conductivity and a decrease in thermal diffusivity. However, the thermal conductivity of composites is still lower than 0.1 W/mK for the most studied samples. The samples show values of acoustic absorption coefficients varying between 0.2 and 0.59 for crushed shiv composites (CSC) at the frequency range (578-1396 Hz) and between 0.2 and 0.73 at the frequency range (662-1396 Hz) for Fibred shiv composites (FSC). It has been observed that the density has a significant effect on the sound absorption coefficient. Increasing the density shifts the acoustic absorption curve towards the low frequencies. Also, decreasing the particle size enhances the sound absorption in the medium frequency range (300-600 Hz). The obtained results are satisfactory for manufacturing these new composites that can be used as thermal and acoustic insulators. Moreover, it offered the best solution for hemp waste management.

Acoustic Panels Inspired by Nature

The article presents the approach to the design process of acoustic panels based on the scientific research. This approach is based on combining the technical and the design competences to develop the innovative product value for the concept of acoustic panels. The article presents the concepts of two new acoustic panels – an absorbing and scattering panel and a panel reflecting sound waves. The first part of the article presents the starting point for the presented project – the acoustic research and the inspiration for both types of presented solutions. Next, the materials possible to use were discussed, which could reproduce the natural acoustic properties of the lava and glacier caves. The next part presents consecutive stages of the product development in a modern form, ensuring the expected acoustic properties. The last part of the article presents a fully functional solution and proposes further research and development directions.

Improving Sound Transmission Through Triple-Panel Structure Using Porous Material and Sonic Crystal

Main aim of this study is to combine the characteristics of the sonic crystal (SC) with acoustic panels and porous materials to improve the sound transmission loss (STL) through the triple-panel structure. SCs cause a bandgap centered around a certain frequency (Bragg’s frequency) due to generation of destructive interference. Initially, an analytical method is developed that extends the previous theory of double-panel structure to predict STL through a triple-panel structure. Finite element (FE) simulations are performed to obtain the STL through the triple-panel, which are validated with the analytical predictions. Various configurations are analyzed using the FE method based on the method of inserting the porous material and SCs between the panels to address the combined effect. STL through the triple-panel structure is compared with that through the double-panel structure having the same total weight and total thickness. It is found that the combined structure of the triple panel and the SC with glass wool as filler gives the best soundproof performance for the same external dimensions. For narrow air gaps, filing with glass wool is more advantageous than inserting one row of SC. In addition, the triple panel combined with a SC has better soundproofing than the two-panel counterparts.