Acoustic Panels Research Articles

ANALYSIS OF THE EFFICIENCY OF ACOUSTIC SCREENS OF DIFFERENT DESIGNS

Various sources of noise in cities and ways to combat them are considered. The effi ciency of two types of acoustic screens is analyzed: single-layer and two-and three-layer. The positive and negative characteristics of various designs of existing acoustic screens are listed. A fundamentally new design of the acoustic screen is described: the panels have a ridge profi le, they are located along the vertical axis of the frame with a step at which the panels above the located ridge cover the top of the lower ridge, the outer surfaces of the panels and their end parts are made of a material that has sound-refl ecting properties, and the inner surfaces of the panels are made of sound-absorbing material. Such an acoustic screen is devoid of the disadvantages inherent in acoustic screens of other structures and is more effi cient. The considered invention allows due to the use of the ridge shape of acoustic panels: prevent the refl ection of sound energy in the direction of noise sources (a small part will be directed upwards); provide almost complete absorption of sound energy as it passes through the channels formed by the ridge panels; provide the same effective protection against noise sources located on both sides of the screen; prevent the formation of snow and ice crust on sound-absorbing surfaces, which ensures the constant eff ectiveness of the screen in diff erent seasons of the year; reduce metal consumption, which will reduce the weight of the structure without reducing its effi ciency and reduce the cost of acoustic screens.

With Our Community, For Our Community: Expanding Possibilities for Engaging in STEM

We examine shifting perceptions of STEM for Latinx teens involved in a “Community STEM” environment. This design shows promise in broadening the definition of science and leveraging expertise of STEM-underrepresented youth. However, these programs are still not typical and merit further investigation. Therefore, we examined a Community STEM project where Latinx teens addressed local noise pollution. Teens documented sound levels, created graphs and maps, presented to stakeholders, and built acoustic panels. Researchers employed an ethnographic perspective, identifying science-relevant roles and artifacts. Artifacts became focal points, promoting reflection on noise pollution, potential solutions, and roles in the project and community.

Prioritizing the noise control methods by using the Analytical Hierarchy Process (AHP) method in an Iranian tire factory.

Noise is a common harmful physical factor in the work environment. This study sought to prioritize noise control methods using the analytical hierarchy process (AHP) in a tire factory. The study, which adopted a cross-sectional, descriptive, analytical design, was conducted in the baking hall of an Iranian tire manufacturing factory in 2018. 4 criteria (namely implementation and maintenance cost, method applicability, method effectiveness and efficiency, and intervention in the process) and 8 alternatives (including reducing individuals' noise exposure time, designing and installing sound isolation chamber for operators, using of earmuffs and earplug simultaneously, changing processes or operational procedures in machinery with excessive noise generation, forming noise control engineering teams, requiring people in charge to quickly fix the leaks and change baking press washers on time, using acoustic panels in the ceiling and walls, and designing and manufacturing silencer and nuzzle for the steam and compressed air outlet of baking press machinery) were selected. Then, to prioritize noise control methods based on objectives, criteria, and alternatives, an AHP questionnaire was developed and completed by domain experts and noise control specialists. Data analysis was performed using Expert Choice V. 11 and Excel. The results showed that the inconsistency rate in all cases was less than 10%, hence the consistency of responses was approved. Based on experts' opinion about the selected criteria, "implementation and maintenance cost" had the highest weight (0.481), while "method effectiveness and efficiency" recorded the lowest one (0.046). With regard to the alternatives, "change in the process" registered the greatest weight (0.193), whereas "individuals' noise exposure time" had the lowest weight (0.046). Based on the final weights, the most appropriate noise control methods in this industry are changing processes in machinery with excessive noise generation, forming noise control engineering team, and manufacturing silencer and nuzzle for the steam and compressed air outlet of baking press machinery. Furthermore, AHP is a suitable approach for prioritizing decisions related to noise control.

Laminated wood composite design with improved acoustic properties

Next-generation laminated wood composites were produced using waste poplar (Populus deltoides) veneer and polyvinyl acetate adhesive. Four experimental groups and one control group were created. Ten-layer laminated wood veneer samples were reinforced with natural rubber (Group A), linoleum (Group B), felt (Group C), and elastomeric sponge (Group D); these materials were used in the fifth adhesive layer (middle layer). The sound absorption coefficients of the control and experimental groups were tested via the impedance tube method, according to ASTM standard E1050 (2006). Attention was paid to the acoustic behavior at low frequencies (63 Hz to 250 Hz), mid frequencies (250 Hz to 2000 Hz), and high frequencies (2000 Hz to 6300 Hz). It was determined that the sound absorption coefficient of the experimental groups considerably increased. It can be suggested that the experimental groups be used as sound absorbing acoustic panels and the control group as sound reflective acoustic panels.

A Century of Use of SOLOMIT Thermal Insulation Panels

This article traces the century-old history of using a thermal and acoustic insulation panel called SOLOMIT. It presents some of Sergei Nicolajewitsch Tchayeff’s patents, on the basis of which production and installation took place. The survey section provides examples of the use of this building component in Australia, Czechoslovakia, France, Germany, the Netherlands, Poland, Russia, the Soviet Union and Spain. It pays attention to applications in the 1950s and 1960s in collectivized agriculture in Czechoslovakia. It also presents the results of measuring the thermal conductivity of a panel sample, which was obtained during the reconstruction of a cottage built in the 1950s and 1960s of the 20th century. Even today, SOLOMIT finds its application all over the world, mainly due to its thermal insulation and acoustic properties and other features, such as low maintenance requirements, attractive appearance and structure and cost-effectiveness.

The effects of acoustical ceiling panel type and penetrations forservices on vertical sound isolation inside buildings

Attenuation of sound transmitting between rooms oriented over one another inside buildings is studied. Transmission loss and sound transmission class were measured by an independent, accredited, acoustics laboratory with and without a variety of modular acoustic ceilings suspended under a baseline concrete floor structure. Ceiling panel material types include stone wool, fiberglass and mineral fiber. Ceilings were tested with and without the presence of service penetrations for supply air diffusers, return air grilles and light fixtures. Some ceilings were also scanned with a sound intensity probe and the resulting color sound maps are used as supplemental method of evaluating both isolation and absorption performance of the individual components of the ceiling systems. Results show that while the effects of ceiling panel type on absorption performance, and thus room acoustics, is substantial, the material type and weight of the ceiling panels do not substantially affect the overall isolation performance of the floor-ceiling assembly.

Evaluation and comparison the properties of acoustic boards made of date palm fiber

Applying acoustic panels made of natural fibers, due to their high biodegradable characteristics, light weight, low density, cheap price and non-toxicity, are proper alternatives to acoustic absorbers made of synthetic fibers. Considering their stance and vast applicability in industry, the possibility of producing them of natural palm fibers with sodium silicate adhesive of 10 and 20% in two 16 and 32 mm thicknesses, 350 and 450 kg/m3 densities, 50 and 100 mm particles length (strands), as variable factors in 16 types of matched panels with 3 repetitions is proposed in this article. The palm-trunk discs constituted the control sample. The effect of variables on sound absorption coefficient was assessed. The effect of variable thickness and adhesive percentage on all frequencies was significant and the effect of density variable on all frequencies except 250 and 2000 Hz was also significant. The effect of particle length was significant except at the 500 Hz frequency. The effects of all variables on porosity were significant. The results of this study suggest that by applying date palm-trunk (an agricultural waste) combined with sodium silicate adhesive, industrial environment-friendly panels can be produced with proper sound absorption coefficient in the field of acoustics. This 32-mm-thick panel was composed of 80% date palm-trunk particles of 50 mm length, 450 kg/m3 density, and 20% sodium silicate adhesive.

Computational homogenization of locally resonant acoustic metamaterial panels towards enriched continuum beam/shell structures

Locally resonant acoustic metamaterial (LRAM) panels are excellent candidates for the low-frequency flexural wave attenuation in thin structures. To enable the efficient analysis and design of LRAM beam/shell structural elements for practical applications, a computational homogenization method for modelling wave propagation phenomena in LRAM panels is presented in this work. The approach is based on the notion of a relaxed separation of scales, which tailors the methodology to the phenomena governed by local resonators embedded in a host medium. The macroscopic LRAM panel is modelled as a thin continuum beam/shell described by proper structural kinematics and momentum balance relations. At the microscale, a LRAM unit cell is considered with lamina-wise in-plane boundary conditions and zero out-of-plane tractions, representing the free top and bottom surfaces of the macroscopic LRAM panel. Under the assumption of linear elasticity, in the relaxed separation of scales regime, the microscale unit cell problem can be represented by the superposition of a static and a dynamic problem, hereby enabling a significant model reduction. As a result, the macroscale effective material properties can be computed once and for all off-line for a given unit cell. In addition, a new macroscale evolution equation emerges describing the effect of the microscale internal dynamics on the macroscopic fields through the introduction of new macroscale enrichment variables, which reflect the modal amplitudes of localized microscale modes. The proposed homogenization methodology reveals a high level of accuracy and numerical efficiency compared to the reference direct numerical simulation (DNS) for all relevant analyses: computation of real and complex dispersion spectra for an infinite LRAM panel, as well as steady-state frequency response and transient behaviour for a finite LRAM panel.

Surface Characteristics and Acoustical Properties of Bamboo Particle Board Coated with Polyurethane Varnish

Using bamboo particle board as a wall divider, a furniture component, or an automotive component with a sound absorber function may be a viable option for architects and engineers seeking to achieve desired acoustical qualities, including noise reduction. However, there is still a dearth of research on the effect of particle board finishing and coatings on acoustical sound absorption and noise reduction qualities. This study, therefore, aims to determine the surface characteristics and acoustical properties of bamboo particle board, coated with polyurethane (PU). The single-layer homogeneous particle boards were constructed using particles classified as fine and coarse with two different board densities, and coated with a high-quality PU lacquer. This study found that the coating treatment of 0.3 mm 0.6 mm succeeded to significantly decrease surface roughness, as well as thickness, swelling, and water absorption, with the thickness coating as a dominant factor compared with board density and board particle size. Adding a PU coating increases sound absorption performance at low frequencies, but significantly reduces acoustical properties at high frequencies. The increase of particle board density leads to the decrease in noise reduction coefficient capability. Results obtained from this study are useful to determine the optimal coating thickness in terms of evaluating acoustical panel products.

Quasi-static indentation and sound-absorbing properties of 3D printed sandwich core panels

The use of 3D printing to produce acoustic panels with good mechanical and acoustic properties was investigated in this paper. Various fiber layups of the fiberglass face sheet and core designs were fabricated and tested for their indentation resistance and acoustic absorption performance. It was found that the bidirectional face sheet layup exhibited the best indentation energy absorption recording 4.2 J, which is 37% more than the 45-degree layout and 66% more than the quasi-isotropic layup. The specific energy absorption of the hybrid honeycomb core is the best among the three core designs recording 404 J/kg, which is 56% higher than the corrugated triangle with horizontal beam core (359 J/kg) and 20% higher than double ellipse core (335 J/kg). Computed-Tomography (CT) scan was used to study the fracture behavior of the sandwich structures. It was found that the bidirectional layup exhibited a different failure mode as compared to the 45-degree and quasi-isotropic layup. In terms of the acoustic properties, the face sheets with various layup patterns have a low acoustic absorption coefficient with minimal differences from each other at low frequencies (500 Hz–3000 Hz) and have higher absorption coefficients with greater differences from each other at frequencies between 3000 Hz–6500 Hz. The absorption curve was significantly affected by the design of the core. The orientation of the core also comes into play if the core is asymmetrical. The hybrid honeycomb sandwich structure was the optimal structure among the three designs for balanced indentation resistance and acoustic insulation.

From mechanics to acoustics: Critical assessment of a robust metamaterial for acoustic insulation application

The increasing popularity of sandwich and composite double panel structures stems from their better sound insulation properties over a wide frequency range with respect to their single panel counterparts. However, in the design of such multi-layer panels particular attention must be paid to the resonance dominated region of the Sound Transmission Loss (STL), where the Mass-Spring-Mass resonance causes a frequency region of poor acoustic performance. In the present contribution, a metamaterial unit cell endowed with an ultra-wide band gap is integrated with faceplates to create a novel acoustic insulation sandwich panel. The panel is realized with a single material and with a properly designed mechanical stiffness that does not affect results in terms of acoustic wave attenuation over a wide frequency range, making at the same time the internal core self-sustained. The STL of the panel is numerically evaluated through a plane wave tube model. The solid-air interaction in terms of resonance frequencies is critically assessed and accurately described by the proposed lumped-parameter model. The model represents a simple tool to predict and optimize the behaviour of the panel in the resonance dominated region of the STL. The acoustic performances of the panel are validated through an experimental campaign on a Nylon prototype, which is 3D printed through Selective Laser Sintering technique.

Does the wall sound different? Variable acoustics in rehearsal rooms using small resonator structures in an acoustic panel.

As the name already states, multipurpose rooms are often used from various people for different intentions like meetings or musical practicing. One example are musical rehearsal rooms, where the acoustic specifications have to meet the requirements of musicians playing different instrument groups. To meet the desire for variable acoustics in a rehearsal room, musicians often like to adjust the room to there personal preferences, what is mostly done by adjusting the frequency dependent room decay curve (T60). Hence, a variable acoustic panel has been developed which consists of several small adjustable resonator structures. In a closed state, the structure acts like a resonator. Although Helmholtz resonators are mostly used at low frequencies, the acoustic panel can address acoustic resonance absorption in the mid-frequency range between 500 Hz and 1.500 Hz. The paper highlights especially the dimensioning of the resonators and its measurements in an impedance tube, a reverberation cabin and a reverberation room. Finally, the prototype of the acoustic panel has been analysed in different rehearsal rooms where musicians examine the panel and T60 differences between the open and closed state of the panel were measured.

Reuse of coffee waste and paper cups for acoustical panel applications in architectural studios

This study has been initiated with an aim of enhancing the acoustical comfort levels in the architectural studios of Bilkent University in Ankara. Initial assessment of the studios by field tests indicated very long reverberation times, supporting the complaints by the students and instructors. In order to be applied in studio environment, acoustical panels are developed out of recycled materials. The increasing coffee demand and consumption of our era have motivated the reuse of both paper cups and coffee waste. The end-product is composed of two layers. The outer layer is out of recycled coffee cups, placed in different arrangements in terms of orientation, size, and spacing. The backing layer is a panel of compressed and kiln-dried coffee grains and tea leaves. The coffee/tea residues are adhered together by using natural binders. In order to determine the best possible alternative of the waste materials with the highest sound absorption performance, different density variations have been explored. Both impedance tube tests and acoustical field measurements are utilized during the process of research and development. Considering the increasing demand for green technology, the layered panel system is proposing cost minimized, environmentally friendly, and biodegradable solutions with improved acoustical and aesthetical values.

The effects of acoustical ceiling panel type and penetrations for services on vertical sound isolation inside buildings

Attenuation of sound transmitting between rooms oriented over one another inside buildings is studied. Transmission loss and sound transmission class were measured by an independent, accredited, acoustics laboratory with and without a variety of modular acoustic ceilings suspended under a baseline concrete floor structure. Ceiling panel material types include stone wool, fiberglass and mineral fiber. Ceilings were tested with and without the presence of service penetrations for supply air diffusers, return air grilles and light fixtures. Some ceilings were also scanned with a sound intensity probe and the resulting color sound maps are used as a supplemental method of evaluating both isolation and absorption performance of the individual components of the ceiling systems. Results show that while the effects of ceiling panel type on absorption performance, and thus room acoustics, is substantial, the material type and weight of the ceiling panels do not substantially affect the overall isolation performance of the floor-ceiling assembly.

Effect of Thickness and Infill Density on Acoustic Performance of 3D Printed Panels made of Natural Fiber Reinforced Composites

ABSTRACT Additive manufacturing (AM) of Natural Fiber-Reinforced Composites through Fused Deposition Modeling is receiving much attention in recent years. AM is very appealing for complex shape structures that can be inconvenient to produce by other methods. In this study, the acoustic panel made from polylactic acid reinforced with wood fiber composite was 3D printed by varying its thickness and infill density. The sound absorption coefficient was measured using an impedance tube. The thin panel with back air gap was found to absorb sound at mid-frequency range resembling the Helmholtz resonator. The absorption performance for the thick panel can be controlled by controlling the infill density of the panel. Customizing the acoustic absorption is therefore possible for panels from biodegradable materials by AM.

Synthesis and Analysis of Biomass based Green Acoustic Shielding Material

The accelerating trend of pollution that stands in the world scenario is noise pollution, the data reported by World Health Organization (WHO) in 2018 which invites the challenges for acoustic engineers and architectural designer in kinds of industries. Designing of acoustic shielding material based on biomass has great importance due to its cutting edge scientific mechanism, structure and variety of applications in various fields. Luffa cyllindrica waste biomass as indigenously available in the most part of the world posses significant contribution in design of acoustic panel due to its versatile, smart and inbuilt networking structure. The nondestructive ultrasonic pretreatment has been used for surface modification with an alcohol blended tartaric acid. The modification in different functional group of the biomass composition and porous activated structure has been confirmed from FTIR and SEM analysis. The presence of inbuilt networking and perforated structure approaches the ideal value of sound absorption coefficient 0.831 with high insulating heat radiation and zero emission of any green house gas to environment can be potentially used as noise shielding material.

Sound Absorbing and Insulating Low-Cost Panels from End-of-Life Household Materials for the Development of Vulnerable Contexts in Circular Economy Perspective

From a construction point of view, neighborhoods with residents living at or below the poverty threshold are characterized by low energy efficiency buildings, in which people live in acoustic discomfort with no viable options for home improvements, as they usually can not afford the materials and labor costs associated. An alternative to this is to use low-cost insulating elements made of non-conventional materials with acceptable acoustic properties. Given that household materials at their end-of-life (EoLHM) are free of costs and available also to the more disadvantaged population, they can be used to build acoustic panels for such contexts. This approach embraces several benefits since it reduces the amount of waste produced, the footprint deriving from the extraction of new raw materials and, by highlighting the potential of the EoLHM, discourages the abandonment of waste. In this paper, the acoustic properties of EoLHM, such as cardboard, egg-cartons, clothes, metal elements and combinations of them, are investigated by means of the impedance tube technique. The measured sound absorption coefficient and transmission loss have shown that EoLHM can be used for the realization of acoustic panels. However, since none of the analyzed materials shows absorbing and insulating properties at the same time, EoLHM must be wisely selected. This innovative approach supports the circular economy and the improvement for the living condition of low-income households.

Effects of Kenaf Fiber Strand Treatment by Sodium Hydroxide On Sound Absorption

ABSTRACT Natural fiber capability as an acoustic panel is subjected to physical properties of the fiber. Chemical treatment was implemented in this study to improve kenaf fiber performances and utilized as a sound absorption material. This research aims to use sodium hydroxide (NaOH) treatment from 1% to 8% concentrations on kenaf fiber. Physical changes on the kenaf fiber strands due to NaOH treatment were observed using Scanning Electron Microscope (SEM). The subsequent effects on sound absorption were measured using Impedance Tube to determine the sound absorption coefficient (SAC) and noise reduction coefficient (NRC) values. Findings show that the diameter of kenaf fiber gradually decreased with the increment of the NaOH concentration. The eliminations of the hemicellulose and lignin layer of the strands causing the decreased of the strand diameter which was proven by FTIR analysis. Results from SAC shows that treated Kenaf fiber using 6%, 7%, and 8% of NaOH obtained higher SAC at high frequency range (>2500 Hz). Those samples obtained 0.67 coefficients for their NRC value. This research concludes the sound absorption capabilities of kenaf absorber was better using thinner strands and the 6% NaOH concentration was the optimum concentration to treat kenaf fiber for sound absorber.

Fabrication of Acoustic Panel from Composites of Coconut Husk Waste Powder and Styrofoam Resin and its Sound Absorption Performance

In this study we have fabricated acoustic panel made from composites of coconut husk waste powder and styrofoam resin. The objectives of this study were to prepare the acoustic panel and to study the effect of amount of styrofoam resin and thickness of the panel on the sound absorption performance of the composites sample. The acoustic panel was prepared by varying the amount of styrofoam resin (i.e. 250 g and 300 g) mixed with 150 g of coconut hust waste powder and the thickness of the panel (i.e. 1 cm and 1.5 cm). The total of four samples were characterized for their sound absorption coefficient. The samples were tested at Physics Laboratory, Faculty of Mathematics and Natural Sciences, Sebelas Maret University, Solo. The sample testing results showed that the amount of styrofoam resin used in the making of the composites panel and the thickness of the panel have played important role in improving the sound absorption coefficient of the composites panel. Based on the sample testing results, among all the four acoustic panel samples, the sample with the best preformance in the noise absorption properties was the Sample B-2 with sound or noise absorption coefficient of 0.77698. Additionally, the sample with the lowest noice reflection coefficient value was the sample with styrofoam resin of 250 g and thickness of 1.5 cm (i.e. Sample A-2), which was about 0.39401 at frequency test of 1600 H.

A broadband acoustic panel based on double-layer membrane-type metamaterials

Low-frequency noise is a growing problem in large structures of modern transportation technologies. In this study, we report a large-scale acoustic panel made of double-layer membrane-type metamaterials (DMAMs) for broadband noise reduction. A complete theoretical model based on the unit cell is fully developed and extended for finite multi-celled membrane-type acoustic metamaterial (MAMs) array. A large-scale acoustic panel constructed from 8 × 8 DMAM unit cells is proposed. To deal with the global compliance of the large-scale support structure, the double-layer panel frame structure with large bending stiffness is designed to shift the global resonances to higher frequencies and provide an efficient way to well maintain the MAM's performance. Moreover, the double-layer configuration further guarantees ultra high transmission loss within the frequency range of interest. Experiments are carried out to validate the analytical and numerical predictions. Excellent transmission loss ranging from 20 to 59 dB within ten third octave bands (0.32–2.5 kHz) is observed, deeply breaking the mass density law. We believe the proposed design and the associated theoretical model could serve as an efficient tool for designing acoustic metamaterial-based panels and soundproof walls with high noise reduction in low/middle frequency regions.