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![Porous zeolite samples with different pore sizes: a 1–2 mm. b 3–5 mm. and c 6–9 mm [197]](publication/359036697/figure/fig14/AS:1152916291362816@1651888072422/Porous-zeolite-samples-with-different-pore-sizes-a-1-2mm-b-3-5mm-and-c-6-9mm-197.jpg)
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Sound absorption mechanism, material modification and structural design of various synthetic fiber materials for industrial noise reduction are reviewed in this paper for the problems of low sound absorption coefficient (SAC) and narrow frequency band of porous materials. Delany-Bazley model and Johnson-Champoux-Allard (JCA) model are widely used t...
Citations
... For this reason, sound scientists have argued that composite structures from sound absorbing materials are more effective in solving such problems. 5 The product mixture formulated in the composite material consists of a fine dispersion of several immiscible phases that appear homogeneous on the macroscopic scale and heterogeneous on the microscopic scale, adding to the previous requirements for the preparation and stability of the mixture. 6 The last group of products has properties outstanding to the properties of each of the materials that generate it. ...
The research investigates the sound absorption properties of potassium polyacrylate (PPA) composites, particularly those augmented with clay and porous hollow glass beads within a hydrogel template. This unique material combination shows promise for efficient sound absorption, relevant in industries requiring effective noise control like acoustic engineering and construction. Experimental assessment focused on measuring the sound absorption coefficient, crucial for quantifying a material's ability to absorb sound energy across various frequencies. Incorporating clay and porous hollow glass beads introduces complexities, emphasizing the need for precise acoustic performance prediction. Collected data from sound absorption coefficient measurements formed the basis for training an Artificial Neural Network (ANN) model. Leveraging the ANN's pattern recognition capabilities, the model learned from diverse composite compositions, enabling accurate prediction of sound absorption coefficients for varying material compositions. This predictive model streamlines material design, offering a systematic approach to tailor composite acoustic characteristics. Integration of machine learning, particularly ANNs, enhances accuracy and expedites material design and optimization, contributing to innovative and customizable sound-absorbing materials for diverse industrial applications.
... The awareness of the harmful effects of noise has promoted the development and use of sound absorbers and insulators in various fields of engineering. Synthetic fibres such as mineral wool and polymeric foams are used as sound absorbers in the construction and building sectors (Liang et al., 2022). Generally, synthetic and mineral materials used as sound absorbers provide high sound absorption, thermal insulation, and better fire-controlling properties than natural fibres. ...
The palm kernel shell is a by-product of palm kernel oil production and is commonly used in the natural biomass energy industry. Coconut husk fibre is extracted from the coconut fruit. To find a use for palm kernel shells and coconut husk fibre, a composite insulator plate was developed by the addition of a binder through a process of grinding, sieving, mixing, heating, hot-pressing and cooling in a mould. An Ahuja speaker AU60 was fixed at one end of a baffled tube and a sound level meter was placed 2 m away from the output to record sound transmission loss at 5s intervals for twenty minutes. The plates of 3, 4, 5, and, 6 mm thickness were fixed in the baffled tube at a distance of 475 mm away from the input one after the other to filter the input sound. The results showed that the setup without a composite insulator recorded the highest noise of 226.8 dB. The average recorded sound transmitted loss was 185.40, 72.47, 74.54, 76.06, and 82.85 dB for no insulator, 3, 4, 5 and, 6 mm composite insulators respectively. The introduction of the 3, 4, 5, and, 6 mm thickness composite insulators resulted in 55.3 %, 59.0 %, 59.8 % and 60.9 % reduction in noise level. The application of agro-waste composite material as a sound insulator in a baffled tube has proven to be effective by 58.7 % on average. The study has confirmed that agro-waste materials can be used in sound insulation applications.
... Sound absorption performance can be achieved through various mechanisms, including porous materials for absorbing sound waves, plate vibration for membrane-based absorption, and resonant mechanisms that exploit air cavity resonance in specific frequency bands. [7][8][9][10][11][12] There are now many materials that can be derived from waste and biomass, such as wood, organic fibers of either plant or animal origin. [13][14][15][16][17] These materials can be used as sound-absorbing materials, and they have low environmental impacts and negative health effects. ...
The subject of the present paper is improving sound absorption properties and protecting the dust generation of ceramic fiber boards. The two‐microphone impedance tube method measured the sound absorption coefficient (SAC) of ceramic fiberboards (CFB) with different shapes and sizes. The wood veneer was used to cover the ceramic fiberboard (VCFB) surface to improve the wall's appearance and prevent dust generation. The step‐shaped ceramic fiberboards with veneer attached (VCFBS) revealed improved SAC (.98, 2000 Hz) compared with CFB and VCFB. The noise reduction coefficient (NRC) and sound absorption average showed a 100% improvement compared to CFB. The surface morphology and air permeability were analyzed using a scanning electron microscope and a capillary flow porometer to correlate with the findings. Furthermore, the porosity and pore diameter of the CFB were also studied to gain a comprehensive understanding of its acoustic properties and sound absorption capabilities. Statistical T‐tests revealed significant variations in the SAC (p ≤ .005). Besides, the obtained SAC was compared with other reported sound‐absorbing materials. These findings suggest that using step‐shaped ceramic fiberboard covered with a wood veneer can significantly absorb sound and improve the living environment. This novel approach offers potential advancements in sound‐absorbing materials for building construction.
... In general, polyurethane (PU) demonstrates stronger sound absorption capabilities in the high frequency range but relatively weaker performance in the middle and low frequency regions. Consequently, various approaches such as density, thickness, structural design and chemical modification enhance the low-frequency sound absorption properties [18]. Thus, the evaluation of sound absorption characteristics of natural fiber-based composite sandwich constructions is to be ascertained for their applications as walls, ceilings, etc., for interior noise control in dwellings, offices, auditoria, theatres and hospitals. ...
Natural fiber-based acoustical materials are widely used as alternative of synthetic acoustical materials. The sound absorption characteristics of material can be instrumental for interior noise control. The study reports the sound absorption characteristics of various sound absorptive materials including microfiber pine wood, Polyethylene Terephthalate polyester acoustic material, polyfiber foam and their composite-based materials tested in Reverberation chambers as per ISO 354:2003 and ASTM C423-2017 with measurement uncertainty of ± 5% at varied air-gaps. The effect of thickness and density of the acoustical materials on sound absorption characteristics were analyzed. It is to observe that addition of glass wool and polyfiber foam enhances the sound absorption characteristics in middle and high frequency range. The study reports the sandwich constructions developed with excellent sound absorption characteristics in middle and high frequency range that can be used for ceilings and walls for noise control .
... Monkova et al., (2020) studied the sound absorption capabilities of 3D printed open porous acrylonitrile butadiene styrene (ABS) samples that were printed with four different lattice structures namely: Cartesian, Starlit, Rhomboid, and Octagonal; and concluded that 3D printed materials were good in sound absorption and could be used industrially as such. Liang et al., (2022) studied the use of inorganic materials, especially their fibers in sound and noise absorption and noted that the acoustic properties of polymers were usually improved by adding fillers, using perforated structures, gradient porous structures, and multiple-layer composite structures. In their study, Qunli Chen et al., (2022) investigated the performance of aluminum silicate fibers and other materials and successfully proved that the pure aluminium silicate fibers performed very well in absorbing low frequency noise compared with the others. ...
In this study, biodegradable materials that could be utilized to reduce noise were examined. Sound absorption test was conducted with an impedance tube. Sawdust, coconut fiber, and expansive clay were used to create test samples. Noise reduction coefficient results for sawdust and expansive clay mixture ranged from 0.24 to 0.62. A mixture of coconut fiber and expansive clay recorded in noise reduction coefficient between 0.31 and 0.58. Coconut fiber mixed with expansive clay recorded noise reduction coefficient ranging from 0.31 to 0.58. The study findings suggests that these materials have good acoustic properties and can therefore be used as alternative noise reduction materials. These findings have important implications in reducing environmental pollution if adopted in the development of noise reducing materials.
... The relationship between the structure and properties of porous materials made of fibers has been extensively investigated [19,20]. In applications where liquids and gases are required to permeate, the void structure of the porous material plays a crucial role, and this information is necessary to analyze the flow within the porous material. ...
The carbon dioxide-assisted polymer compression method is used to create porous polymer products with laminated fiber sheets that are crimped in the presence of carbon dioxide. In this method, fibers are oriented in the sheet-spread direction, and the intersections of the upper and lower fibers are crimped, leading to several intersections within the porous product. This type of orientation in a porous material is anisotropic. A dye solution was injected via a syringe into a compression product made of poly(ethylene terephthalate) nonwoven fabric with an average fiber diameter of 8 μm. The anisotropy of permeation was evaluated using the aspect ratio of the vertical and horizontal permeation distances of a permeation area. The aspect ratio decreased monotonically with decreasing porosity; it was 2.73 for the 80-ply laminated product with a porosity of 0.63 and 2.33 for the 160-ply laminated product with a porosity of 0.25. A three-dimensional structural analysis using X-ray computed tomography revealed that as the compression ratio increased, the fiber-to-fiber connection increased due to the increase in adhesion points, resulting in decreased anisotropy of permeation. The anisotropy of permeation is essential data for analyzing the sustained release behavior of drug-loaded tablets for future fabrication.
... Porous materials are often applied in noise mitigation or reverberation control tasks, due to their sound absorption capabilities [1,2]. These absorption properties, e.g. the frequency-dependent sound absorption coefficient, are most commonly measured under laboratory conditions using standardized two- 5 microphone impedance tube methods [3, 4,5]. ...
... Noise refers to sound that interferes with the surrounding living environment, such as industrial noise [1], construction noise [2], traffic noise [3] and social activity noise [4]. Normally, the actual noise is in a wide frequency region [5], which requires the utilized sound absorber to be broadband [6][7][8][9][10]. ...
... The theoretical sound absorption coefficient of the acoustic metamaterial of the TA-MPCHR can be obtained according to electro-acoustic theory [8,9,13,17], as shown in Equation (1). Here, α is the theoretical sound absorption coefficient, Z is the total acoustic impedance of the metamaterial cell, ρ 0 is the density of the air and c 0 is the sound velocity in air. ...
The variable noise spectrum for many actual application scenarios requires a sound absorber to adapt to this variation. An adjustable sound absorber of multiple parallel-connection Helmholtz resonators with tunable apertures (TA–MPCHRs) is prepared by the low-force stereolithography of photopolymer resin, which aims to improve the applicability of the proposed sound absorber for noise with various frequency ranges. The proposed TA–MPCHR metamaterial contains five metamaterial cells. Each metamaterial cell contains nine single Helmholtz resonators. It is treated as a basic structural unit for an array arrangement. The tunable aperture is realized by utilizing four segments of extendable cylindrical chambers with length l0, which indicates that the length of the aperture l is in the range of [l0, 4l0], and that it is tunable. With a certain group of specific parameters for the proposed TA–MPCHR, the influence of the tunable aperture with a variable length is investigated by acoustic finite element simulation with a two-dimensional rotational symmetric model. For the given noise spectrum of certain actual equipment with four operating modes, the TA–MPCHR sample with a limited total thickness of 40 mm is optimized, which is made of photopolymer resin by the low-force stereolithography, and its actual average sound absorption coefficients for the frequency ranges of 500–800 Hz, 550–900 Hz, 600–1000 Hz and 700–1150 Hz reach 0.9203, 0.9202, 0.9436 and 0.9561, respectively. Relative to common non-adjustable metamaterials, the TA–MPCHR made of photopolymer resin can reduce occupied space and improve absorption efficiency, which is favorable in promoting its practical applications in the noise pollution prevention.
... The methods for noise mitigation can typically be grouped into three major categories: (i) passive, (ii) active, and (iii) hybrid [2][3][4]. As the most extensively used method effective for mid-and high-frequency airborne noise mitigation, the passive approach can absorb noise by passively converting acoustical energy into heat dissipation, in which the working mechanisms include viscous effect, thermal effect, and material damping [5][6][7][8][9]. The viscous effect is the cause of the adherence of the fluid in the interface with the solid. ...
Airborne sound absorption in porous materials involves complex mechanisms of converting mechanical acoustic energy into heat. In this work, the effective piezoelectric properties of polyethylene ferroelectret foams on sound absorption were investigated by comparable samples with and without the piezoelectric response. Corona poling and thermal annealing treatments were applied to the samples in order to enable and remove the piezoelectric property, respectively, while the microstructure and the mechanical properties remained substantially unchanged. The effective piezoelectric properties and airborne sound absorption coefficients of the polyethylene foam samples before and after material treatments were measured and analyzed. Our experimental results and theoretical analysis showed that the open-cell ferroelectret polymer foam with an effective piezoelectric property provides an additional electromechanical energy conversion mechanism to enhance the airborne acoustic absorption performance.
... The first is the empirical model with few parameters, which is relatively easy to establish. The most representative empirical model is the Delany-Bazley model, related to the airflow resistivity of the materials, but it can only be employed for predicting the acoustic behaviors of porous materials in the frequency range of 250-4000 Hz [45,46]. In order to obtain more accurate predictions, some studies made specific corrections to the Delany-Bazley model and developed several new models. ...
Noise is considered severe environmental pollutant that affects human health. Using sound absorption materials to reduce noise is a way to decrease the hazards of noise pollution. Micro/nanofibers have advantages in sound absorption due to their properties such as small diameter, large specific surface area, and high porosity. Electrospinning is a technology for producing micro/nanofibers, and this technology has attracted interest in the field of sound absorption. To broaden the applications of electrospun micro/nanofibers in acoustics, the present study of electrospun micro/nano fibrous materials for sound absorption is summarized. First, the factors affecting the micro/nanofibers’ sound absorption properties in the process of electrospinning are presented. Through changing the materials, process parameters, and duration of electrospinning, the properties, morphologies, and thicknesses of electrospun micro/nanofibers can be controlled. Hence, the sound absorption characteristics of electrospun micro/nanofibers will be affected. Second, the studies on porous sound absorbers, combined with electrospun micro/nanofibers, are introduced. Then, the studies of electrospun micro/nanofibers in resonant sound absorption are concluded. Finally, the shortcomings of electrospun micro/nano fibrous sound absorption materials are discussed, and the future research is forecasted.
