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•Influence of fiber length on sound absorption property of Jute fiber.•Influence of surface modification of jute fiber on souund absorption property.•Evaluation of lumen structure of ...treated and untreated fiber through SEM image analysis.
The use of plant fibers for acoustic applications in the industrial sector is increasing nowadays due to: their porous nature, hollow lumen structure, and the presence of Nano-fibrils. The current investigation aims to analyze the influence of jute fiber length and various chemical treatments on the sound absorption property. The sound absorption coefficient was measured by the Impedance tube method. From the results, it was found that 20 mm fiber length has the uppermost sound absorption coefficient at all frequencies, due to the increase in the number of air cavities and nanofibrils. Further, the 20 mm length fiber was surface modified by NaOH, NaHCO3 and Cr2SO4 respectively and the sound absorption coefficient of the surface modified fibers was analyzed. The result showed that among the various chemical treatments, alkali treated fiber has the maximum sound absorption coefficient than the other treated fibers. The SEM images revealed that the chemical modification causes changes in the morphology of fibers. In addition, the comparative study of the experimental and theoretical sound absorption coefficient showed good agreement between them.
Introduction: In recent years tend to use of natural fibers has increased in making sound absorbers. Fiber-based natural materials have low density, low production costs, and are biodegradable. ...Material and Methods: In this study, the effect of nanoclay and the behavior of the nanocomposite specimens containing tea waste, polypropylene, and nanoclay in the sound absorption coefficient are investigated. Results: The results showed the sound absorption coefficient increases by increasing the tea waste weight percent of the polypropylene. 60% increase in tea waste has a special role in the absorption of sound waves at a frequency of 1000 Hz and 2500 to 6300 Hz frequency range as the TW60 N5 sample has the sound absorption coefficient 0.94 and 0.84 in 1000 and 6300 Hz frequencies, respectively. Comparison of the sound absorption coefficient of composite and nanocomposite showed that sound absorptions increase by adding nanoclay to the 5%, at frequencies above 2000 Hz. Conclusion: Tea waste-based sound absorbers can be used in noise control due to the high acoustic absorption and no harmful effects on human health.
•Introduce a novel approach to transform agricultural waste into functional construction materials.•Offers an in-depth analysis of the structural, thermal, and acoustic properties of the developed ...panels.•Utilizing rice straw, we address the issue of air pollution in regions with intensive agricultural activities, contributing to cleaner air and healthier living environments.
To address the pressing need for sustainable building materials, this study introduced an innovative and eco-friendly approach to manufacturing thermal-acoustic panels, utilizing agricultural waste with rice straw as the primary material. Paper pulp (PP) and Persea kurzii (PK) were used as non-chemical binders at ratios of 50:50, 60:40, 70:30, and 80:20. After mixing, all the samples were subjected to heat-free hydraulic compression at 5 bars to evaluate their physical, mechanical, thermal, and acoustic properties. Increasing the proportion of the binder directly impacted panel density and flexural strength while also inversely affecting porosity. The PK binder had a low thermal conductivity value of 0.040 W/mK, proving it was a good thermal insulator with a high sound absorption coefficient, especially at higher frequencies. The RSPP-4 panel had the highest noise reduction coefficient (0.51) and absorbed low frequencies, suggesting its potential for noise reduction. Microscopic analysis provided further insight into panel surface characteristics. PP exhibited a smooth surface with a continuous fiber weave that did not obscure the pores, while PK consisted of particles. The correlation between surface characteristics and acoustic performance, especially at high frequencies, underscored the intricate balance between material properties. Research results can be applied in the construction industry to develop sustainable building materials that offer superior thermal and acoustic properties. These thermal-acoustic panels can effectively utilize agricultural waste and show potential as environmentally friendly construction materials to enhance indoor comfort and acoustics in various building environments.
A technique is proposed that uses a multi-scale approach to calculate transport properties of compressed felts using only image analysis and numerical calculations. From the image analysis fiber ...diameter distribution and fiber orientation are determined. From a known porosity and the latter two characteristics, two representative elementary volumes (REV) are constructed: one based on the volume-weighted average diameter and one on an inverse volume-weighted average diameter. Numerical calculations on the former showed that it correctly estimates viscous and thermal permeabilities, while the latter correctly estimates tortuosity and viscous and thermal characteristic lengths. From these calculations, micro-macro analytical expressions are developed to estimate the transport properties of polydisperse composite felts based solely on open porosity, fiber diameter polydispersity, and fiber orientation. Good agreements are obtained between analytical predictions and measurements of transport properties. The predicted transport properties are also used in the Johnson–Champoux–Allard–Lafarge (JCAL) equivalent fluid model to predict the sound absorption coefficient of the felts. Excellent agreements are obtained with impedance tube measurements.
•Investigating transversely isotropic polydisperse fibrous media.•Modeling fiber microstructures for transport and sound absorbing properties.•Two microscale models established using volume and inverse-volume-weighted diameters.•Semi-analytical model predicts accurately for a wide range of porosities.
•Post-consumer denim was collected from municipal waste sorting plants and recycled.•Efficient sound-absorbing construction material was produced.•Prediction of sound absorption was performed using ...logarithmic and JCA models.•Recycled denim composites successfully compete with commercial glass wool samples.•Recycled denim composites are environmentally friendly and economically viable.
Recently, a growing interest has been focused on utilizing alternative recycled sound-absorbing construction materials. This study investigates phenolic resin-bonded recycled denim as a potential replacement to synthetic sound absorbers. To this end, the discarded denim was collected from municipal waste sorting plants and shredded to back down into fiber form. Solid novolac resin and fibers were fed to the air-laid machine. The hybrid structures were then introduced to an oven to cure the resin and form an integrated flexible structure. Nonwoven composites at different bulk densities (61–102 kg/m3) and resin contents (10–35%) were produced. The sound absorption coefficient (SAC) of composite samples was determined using the impedance tube method. The relationship between SAC versus frequency was modeled using a logarithmic regression and the phenomenological model of Johnson-Champoux-Allard (JCA). Additionally, the noise reduction coefficient (NRC) values of the samples were compared with those of some commercially available glass wool nonwovens of the same physical properties. The results showed that the mechanism of sound absorption for samples is viscosity resistance, in which SAC at low frequencies is low, however at high frequencies is quite significant. The results of the statistical analysis confirmed that both the bulk density and resin content have a significant effect on the SAC. It was found that SAC rises with increasing the areal density and bulk density, and this raise is more pronounced at higher bulk densities. It was also observed that for samples of the same bulk density, SAC increases with increasing the resin content. The results indicated that resin-bonded recycled denim composites could successfully compete with commercial glass wool samples for noise control, apart from being environmentally friendly and economically viable.
•Micro-perforated panel absorbers (MPPA) are fabricated using 3D printing technology.•Acoustic properties of composite MPPA layers are measured by using impedance tube method.•The measured sound ...absorption coefficient results are theoretically validated.•Acoustic properties variations with perforation ratio and depth of air cavity are discussed.•The results obtained in this paper provided a new approach for the fabrication of composite sound-absorbing structures.
This paper investigates the acoustic absorption capability of a multilayer micro-perforated panel absorber (MPPA) whose front layer is produced by additive manufacturing. The MPPA layers are printed using a polymer material, where the different hole spacing is used to create different perforation ratios. The sound absorption coefficients are experimentally measured by using an impedance tube test, to investigate the effects of the perforation ratio and the depth of an airgap behind the MPPA. Also, a porous sound absorbing material layer is attached behind the MPPA layer in order to produce a multilayer acoustic absorber. The measurement results are compared to a theoretical approach. The comparisons show that the measured sound absorption coefficients agree fairly well with the theoretical model. The use of a porous sound absorbing material behind the MPPA broadens the frequency bandwith of the multilayer acoustic absorber. The frequency of the maximum sound absorption coefficient can be varied, by altering the perforation ratio of the MPPA and/or the depth of the airgap behind the panel.
•Designed and developed a 3D printed microperforated sound-absorbing thermoplastic sandwich structure.•Microperforated folded core structure improves sound absorption (99 %) at low ...frequencies.•Addition of GO-coated PU foam to folded core structure enhanced sound absorption at high frequencies.•GO-coated PU added folded core enhanced the mechanical performance.•The multifunctional composite structure is a candidate for various applications.
This study introduces a novel sound-absorbing sandwich structure with a folded core, created through 3D printing technology, to address the challenge of weak sound absorption in the low-frequency range in sound absorption materials (SAMs). The structure comprises chopped carbon fiber–dispersed thermoplastic polyamide (CF-PA), continuous carbon fiber (CCF) filaments, and polyurethane (PU) foam coated with graphene oxide (GO). Simulation studies revealed that optimized structural parameters and microperforation diameters resulted in enhanced sound absorption coefficient (SAC) of 99 % or more at 1250 Hz, within the low-frequency range (160–1600 Hz). The GO-coated PU foam SAMs demonstrated excellent sound absorption performance measured in the high-frequency range (1600–6000 Hz), achieving 99 % SAC at 2400 Hz. Furthermore, the manufactured folded core structure exhibited outstanding sound absorption performance, achieving SAC of 99 % at 732 Hz measured in the low-frequency (160–1600 Hz) band and 99 % at 600 Hz, showcasing broad absorption capabilities measured in the high-frequency band (160–6000 Hz). Additionally, a flatwise compression test on the structure filled with GO-coated PU foam demonstrated a 32 % improvement in compressive load, indicating the structure’s versatility for various applications.
•Fibres from the oil palm empty fruit bunch (OPEFB) are studied for its sound absorption performance.•OPEFB fibre sample with thickness of 40mm can have absorption coefficient of 0.9 in average above ...1kHz.•OPEFB fibre shows similar sound absorption performance with the commercial synthetic rock wools at the same thickness.
This paper discusses the utilisation of fibres from the oil palm empty fruit bunch (OPEFB) to be an alternative natural acoustic material. The study was carried out by fabricating samples from raw OPEFB fibres with different densities and thicknesses to observe their effects on the sound absorption performance. It has been demonstrated that the sound absorption performance can be improved by increasing the thickness of the sample and also by having optimum densities of fibres. In particular for lower frequencies, this can be achieved by introducing air cavity gap behind the fibre samples. Measurement of the normal incidence absorption coefficient in an impedance tube based on ISO 10534-2 found that the OPEFB fibres can have absorption coefficient of 0.9 on average above 1kHz. The sound absorption performance of OPEFB fibres is also shown to be comparable to that of the commercial synthetic rock wools.
Sound absorbing materials for noise control are distinguished due to their high efficiency in sound absorption. However, many of these materials are of synthetic origin and cannot be disposed of as ...solid waste in nature or incinerated by industry, because they are very polluting. Natural fibers can be an important alternative to replace these materials in noise control area. The present work aims to evaluate the sound absorption coefficient of three natural fibers: sisal, coconut husk and sugar cane with two empirical and one experimental method. Ten samples of each material with 20, 30 and 40 mm in thickness were evaluated. The empirical models applied in the analyzes were published by Delany and Bazley in 1970 and Allard and Champoux in 1992. The Allard and Champoux method is a simplified approach to minimize Delany and Bazley inconsistencies at low frequencies. The predictions of the empirical methods were compared with an experimental analysis using the transfer function method based on the ASTM 1050-12 standard. Finally, an inverse methodology was presented to optimize the coefficients of the Delany and Bazley model to better represent the studied fibers.
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•A multilayered graphene oxide-impregnated polyurethane foam (GO-PU) is proposed to maximize the sound absorption coefficient (SAC).•The average SAC was 0.90 for a 54.6 mm thick ...material, which showed the best sound absorption performance at a given thickness.•A theoretical method for deriving the maximum SAC was developed by modifying the elastic porous materials theory of Bolton et al.•Maps of the optimal arrangement by simulation provided a convenient way to apply the results of this study to various thicknesses.•Great potential of GO as an acoustic material was presented, and a novel method to control the acoustic performance was proposed.
A multilayered graphene oxide-impregnated polyurethane (GO-PU) foam structure is proposed to maximize the sound absorption coefficient (SAC). The sound absorption properties of each PU layer were controlled via GO impregnation. The optimal multilayered structure was derived via theoretical predictions using matrix calculations. The elastic porous materials theory of Bolton et al. was applied to theoretical modeling of the sound-absorbing materials. The developed routine predicted the SAC with high accuracy for single and multilayered designs. The impregnation effect of GO was enormous and improved the average SAC by up to 153 % compared with the original PU. It is encouraging that the average SAC was improved by up to 49 % by simply optimizing the layer arrangement with the same amount of GO impregnation. Notably, the average SAC above 500 Hz of the optimized 54.6-mm -thick (±0.4 mm) GO-PU multilayered structure was enhanced to over 0.9. These remarkable results were verified by theoretical calculations and experiments.
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