Faculty Publications

Now showing 1 - 4 of 4

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 Ltd
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.
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.
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

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