The current study deals with the analysis of sound absorption characteristics of foxtail millet husk powder. Noise is one the most persistent pollutants which has to be dealt seriously. Foxtail millet is a small seeded cereal cultivated across the world and its husk is less explored for its utilization in polymer composites. The husk is the outer protective covering of the seed, rich in silica and lingo-cellulose content making it suitable for sound insulation. The acoustic characterization is done for treated foxtail millet husk powder and polypropylene composite panels. The physical parameters like fiber mass content, density, and thickness of the composite panel were varied and their influence over sound absorption was mapped. The influence of porosity, airflow resistance, and tortuosity was also studied. The experimental result shows that 30-mm thick foxtail millet husk powder composite panel with 40% fiber mass content, 320 kg/m density showed promising sound absorption for sound frequency range above 1000 Hz. We achieved noise reduction coefficient (NRC) value of 0.54. In view to improve the performance of the panel in low-frequency range, we studied the efficiency of incorporating air gap and rigid backing material to the designed panel. We used foxtail millet husk powder panel of density 850 kg/m as rigid backing material with varying air gap thickness. Thus the composite of 320 kg/m density, 30-mm thick when provided with 35-mm air gap and backing material improved the composite's performance in sound frequency range 250 Hz to 1000 Hz. The overall sound absorption performance was improved and the NRC value and average sound absorption coefficient (SAC) were increased to 0.7 and 0.63 respectively comparable with the commercial acoustic panels made out of the synthetic fibers. We have calculated the sound absorption coefficient values using Delany and Bezlay model (D&B model) and Johnson-Champoux-Allard model (JCA model) and compared them with the measured sound absorption values.
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http://dx.doi.org/10.3390/ma13225126 | DOI Listing |
Materials (Basel)
December 2024
School of Power and Energy, Nanchang HangKong University, 696 South Fenghe Avenue, Nanchang 330063, China.
The sound absorption structure of a microperforated plate has many advantages and has great potential in the field of noise control. In order to solve the problem of broadband sound absorption of microperforated plates, a series acoustic structure of microperforated plates of unequal cross-section was designed based on the traditional microperforated plate series acoustic structure. Compared with the traditional series structure, the sudden change of cross-section increases the sound energy dissipation and greatly improves the sound absorption performance.
View Article and Find Full Text PDFJASA Express Lett
January 2025
Key Laboratory of Noise and Vibration Research, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190,
Through non-dimensional analysis of the nonlinear sound absorption characteristics of rigid-porous layers, the results indicate that the nonlinear sound absorption trend of a porous layer (PL) at high sound pressure levels (SPLs) mainly depends on the state of flow resistance matching. When a PL is in an under-matched state, the sound absorption coefficient (SAC) will initially rise to a maximum and then gradually decline as SPL increases. Comparatively, when it is in an over-matched state, the SAC will decrease monotonically.
View Article and Find Full Text PDFArch Toxicol
January 2025
Cosmetics Europe, Brussels, Belgium.
Grouping of chemicals has been proposed as a strategy to speed up the screening and identification of potential substances of concern among the broad chemical universe under REACH. Such grouping is usually based on shared structural features and should only be used for the prioritization objectives. However, additional considerations (as well as structural similarity) are needed, e.
View Article and Find Full Text PDFSci Rep
December 2024
Faculty of Mechanical Engineering, Department of Machining, Assembly and Engineering Metrology, VSB-Technical University of Ostrava, Ostrava-Poruba, 708 00, Czech Republic.
The aim of this work is to investigate the sound absorption properties of open-porous polyamide 12 (PA12) structures produced using Selective Laser Sintering (SLS) technology. The examined 3D-printed samples, fabricated with hexagonal prism lattice structures, featured varying thicknesses, cell sizes, and orientations. Additionally, some samples were produced with an outer shell to evaluate its impact on sound absorption.
View Article and Find Full Text PDFMacromol Rapid Commun
December 2024
Department of Mechanical and Manufacturing Engineering, University of Cyprus, 1 Panepistimiou Avenue Nicosia, Aglantzia, 2109, Cyprus.
Sound absorption plays a crucial role in addressing noise pollution that may cause harm to both human health and wildlife. To tackle this environmental issue, the implementation of natural-based sound absorbing materials attracts considerable attention in the last few years. In this study, sound absorbing, eco-friendly composites are produced by combining a 3D natural sponge namely Luffa Cylindrica (LC) with cellulose acetate (CA) microfibrous layers that are fabricated through electrospinning.
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