Faculty Publications
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Item Sound absorption and transmission loss characteristics of 3D printed bio-degradable material with graded spherical perforations(Elsevier Ltd, 2022) Sailesh, R.; Yuvaraj, L.; Doddamani, M.; Mailan Chinnapandi, L.B.M.; Jeyaraj, J.The influence of spherical bubble perforations and their grading on acoustic characteristics of a 3D printed bio-degradable material is investigated. Samples with spherical bubble perforations of different sizes are distributed either uniformly or graded across the specimen thickness. A sample having typical cylindrical perforations is also analyzed for comparative analysis. Sound absorption (SA) and sound transmission loss (STL) characteristics are estimated by the impedance tube method. The results reveal that the SA of all functionally graded (FG) perforations is higher at low frequencies. The SA and bandwidth are higher for a specimen with uniform, lower diameter bubbles at higher frequencies. The STL of FG perforations is highest among the specimens, and the difference increases significantly with frequency. The numerical and experimental results match a high degree of accuracy. FG perforations exhibited superior performance for both SA and STL. The proposed graded spherical porosity can be effectively utilized in soundproofing applications across building and transportation sectors. © 2021 Elsevier LtdItem Sound absorption and transmission loss of 3D printed wood fibre reinforced poly lactic acid with functionally graded perforations(Taylor and Francis Ltd., 2024) Sailesh, R.; Doddamani, M.; Mailan Chinnapandi, L.B.; Yuvaraj, L.; Pitchaimani, J.The effect of wood fibre reinforcement on acoustic properties of 3D printed poly lactic acid samples having varying cross-section perforation and functionally graded spherical perforations is presented. Acoustic characteristics like sound absorption as well as transmission loss are obtained using an impedance tube setup. Results revealed the benefits due to the addition of wood fibres in PLA improved samples’ sound transmission loss characteristics significantly. The sound absorption curve peaks shifted to low-frequency regions which are favourable to living beings. The material can be used in acoustic insulation for structural and transportation applications, especially where eco-friendliness and aesthetics are of major concern. © 2023 Informa UK Limited, trading as Taylor & Francis Group.Item Acoustic characterization of natural areca catechu fiber-reinforced flexible polyurethane foam composites(John Wiley and Sons Inc, 2024) Mb, S.; Kumar, G.C.M.; Pitchaimani, J.The development of acoustic absorbers from natural resources is a novel approach in acoustics. In the current study, the effect of unprocessed raw areca fiber (AF) particle reinforcement on the sound absorption (SA) behavior of polyurethane (PU) foam composites is investigated. Influences of fiber weight percentage and graded distribution of fiber with varying fiber weight percentage on the SA coefficient (SAC) of the composite foams are examined through the impedance tube approach. Morphological studies are carried out with the help of FESEM images to investigate the acoustic energy dissipation mechanism of PU foam and its composites. It is found that the SA capability of the composite foam is enhanced by increased fiber weight percentage, graded distribution of fiber wt%, varying sample thickness, and air cavity length. In general, PU-AF composite specimens show a peak SA value of 0.95 around 450 Hz, which is not the case for other natural fiber results available in the literature. Theoretical results predicted using the JCA (Johnson-Champoux Allard) model agree with the experimental results. © 2023 Wiley Periodicals LLC.Item 3D Printed Thick Micro-Perforated Panel with Graded Perforation for Practical Wall Sound Absorption Applications(Springer, 2024) Shafeer, M.; Pitchaimani, J.; Doddamani, M.In recent years, noise pollution has been recognized as a significant environmental issue, and using sustainable materials as sound-absorbing building materials have drawn considerable attention. The influence of graded perforations on the acoustic characteristics of a 3D printed bio-degradable thick micro-perforated panel (MPP) having graded perforation and made of Poly Lactic Acid is presented. Thicker panels are considered owing to the mechanical strength required for practical wall applications. A fused deposition modeling based 3D printer is used to fabricate the MPPs with graded cylindrical perforations and different patterning of perforations. The sound absorption coefficient is measured using the impedance tube technique and compared with theoretical results obtained using an equivalent electro-acoustic model. Results revealed that for normal incidence, the absorption coefficient is only dependent on the overall perforation ratio of the panel, irrespective of the perforation gradation and patterning of perforation. This gives the freedom to distribute the perforation aesthetically for interior wall application. This work also proposes the effective perforation ratio approach to predict the sound absorption coefficient (SAC) of MPPs with graded perforation. For multi-thickness MPPs and MPPs with linearly graded thickness, improved sound absorption characteristics were observed both in terms of bandwidth of absorption and peak value of SAC compared to the conventional constant thickness MPPs. © Australian Acoustical Society 2023.Item Sound absorption performance of natural areca plant husk fibers: Experimental and theoretical study(SAGE Publications Ltd, 2024) Mb, S.; Gc, M.K.; Pitchaimani, J.Fibers extracted from plant wastes can be used for sound absorption (SA) applications in vehicles due to its lightweight and porosity. The SA capability of raw areca fibers bundle (RAFB) as a function of the density and thickness of the test specimen is analyzed. Experimental results obtained using the impedance tube approach reveal that an increase in the specimen bulk density and thickness improves the SA capability of RAFB. Similarly, hollow air volume behind the sample enhances the SA in the lower frequency range. Theoretical results predicted using the Johnson–Champoux–Allard model match well with the experimental predictions. The ability of the RAFB to absorb sound is demonstrated to be equivalent to other commercially available natural and artificial fibers by comparing the results available in the literature. © IMechE 2023.Item Thermal stability and sound absorption in perforated areca sheath-epoxy composite materials(Springer Science and Business Media B.V., 2025) Varghese, L.; Kumar, G.C.The present work emphasizes developing epoxy composites using areca sheath particulates, focusing on improving the thermal and acoustic properties. These composites are developed using conventional methods, and followed by surface modification by different types of perforations using pin perforation techniques. The sound absorption characteristics of these specimens were evaluated using an impedance tube, while thermal stability through thermogravimetric analysis and microstructural properties were analyzed. The results indicate that composite specimens with only half of the area perforated with 1 mm diameter holes demonstrate a superior sound absorption range compared to other specimens. The influence of perforation patterns on specimen surfaces was also studied. Additionally, the thermogravimetric analysis of composites reveals that the developed materials possess significant thermal stability, making them more suitable for thermal and acoustic applications in public buildings and auditoriums than other lightweight composites. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.Item Experimental investigation of embedded neck designs and core geometries for enhanced low-frequency sound absorption in 3D printed micro-perforated panels(Elsevier Ltd, 2025) Mohamed Shafeer, P.P.; Pitchaimani, J.; Doddamani, M.This study presents an experimental investigation into the acoustic performance enhancement of micro-perforated panel (MPP) based liners through structural modifications involving embedded necks and engineered core geometries. All samples were produced through fused deposition modeling with polylactic acid as the filament material. Sound absorption coefficients were measured using an impedance tube method (ASTM E1050) in a 50–1600 Hz frequency range. Initially, cylindrical necks of varying lengths were analyzed to assess the impact of neck extension on sound absorption, particularly in the low-frequency range. This was followed by evaluating non-cylindrical embedded neck profiles (converging, diverging, converging-diverging, and diverging-converging) for a fixed neck length. Then the effect of engineered core topologies, including square, hexagonal, re-entrant, and hybrid geometries, is studied on broadband absorption. Finally, selected core designs were combined with embedded necks to examine the synergetic effects. Incorporation of a cylindrical embedded neck results in shifting of peak absorption to lower frequency (328 Hz for 5 mm), with a weight reduction of 37.5 % compared to the typical MPP. The peak value and the frequency are not sensitive to different types of non-cylindrical embedded necks, and there is about 20 % improvement in the bandwidth with a trade-off of approximately 100 Hz shift in peak frequency towards the higher frequency side. Structured cores enhanced peak frequency (up to 25 %) and bandwidth (up to 10 %). Combined configurations exhibited limited synergistic enhancement, likely due to resonator interference effects. This study introduces a novel geometric strategy for tuning acoustic performance via coordinated neck and core design variations, enabling compact, lightweight, and tunable acoustic liners for low-frequency absorption. © 2025 Elsevier Ltd