Faculty Publications
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Item Worldwide, increasingly stringent regulations are coming into force, limiting the exposure of workers to industrial noise. Industrial noise and its consequences are thus growing in importance to employers, local and central government officials, trade unions, occupational hygienists and physicians and insurers. India is not an exception to this. The mining industry in India is facing serious problems over noise due to increasing demand for minerals for which large capacity machines are being deployed producing high noise levels. To know the status and to control the noise, the S&T Department of the Ministry of Coal, Government of India sponsored a research project in the area of noise pollution and its control for opencast projects. To start with, a detailed literature survey was carried out in the area of noise pollution and its control in the mining industry, embracing equipment like from Heavy Earth Moving Machinery (HEMM), compressors, workshops, pneumatic drills, processing plants etc, to know the quantum of work done in and worldwide. The various aspects studied In this project were the daily noise dose and/or noise exposure level of the operators of various types of heavy earth moving machinery and its assessment, noise characteristics at different operating conditions of the machine, analysis of noise coming out from different parts of the machine, analysis of noise at different distances from the machine for different frequency components and the most important one i.e., impact of periodic maintenance on the noise characteristics of machines and to find out with which maintenance schedule there is maximum fluctuation in the noise level and to evolve a technique for attenuating the noise generated from these machines as well as to reduce the operator's exposure to high noise levels. This paper highlights the results of this research project.(Multi-Science Publishing Co. Ltd, Noise analysis of heavy earth moving machinery deployed in opencast mines and development of suitable maintenance guidelines for its attenuation - Part 3) Vardhan, H.; Rao, Y.V.; Karmakar, N.C.2004Item Worldwide, increasingly stringent regulations are coming into force, limiting the exposure of workers to industrial noise. Industrial noise and its consequences is thus growing in importance to employers, local and central government officials, trade unions, occupational hygienists and physicians and insurers. India is not an exception for this. The mining industry in India is facing serious problem of noise due to increasing demand for minerals for which large capacity machines are being deployed producing high noise levels. To know the status and to control the noise, the S&T Department of the Ministry of Coal, Government of India sponsored a research project in the area of noise pollution and its control for opencast projects. To start with, a detailed literature survey was carried out in the area of noise pollution and its control in the mining industry, embracing equipment like from Heavy Earth Moving Machinery (HEMM), compressors, workshops, pneumatic drills, processing plants etc., to know the quantum of work done in India and worldwide. The various aspects studied in this project were the daily noise dose and/or noise exposure level of the operators of various types of heavy earth moving machinery and its assessment, noise characteristics at different operating conditions of the machine, analysis of noise coming out from different parts of the machine, analysis of noise at different distances from the machine for different frequency components and the most important one i e, impact of periodic maintenance on the noise characteristics of machines and to find out with which maintenance schedule there is maximum fluctuation in the noise level and to evolve a technique for attenuating the noise generated from these machines as well as to reduce the operator's exposure to high noise levels. This paper highlights the results of this research project.(Multi-Science Publishing Co. Ltd, Noise analysis of heavy earth moving machinery deployed in opencast mines and development of suitable maintenance guidelines for its attenuation - Part 1) Vardhan, H.; Rao, Y.V.; Karmakar, N.C.2004Item An experimental study was carried out to investigate the principal sources of sound from heavy earth-moving machinery, namely a bulldozer and a front-end loader. Major sound sources were the exhaust and air inlet for the engines and the engine cooling fan on the bulldozer. Sound from the exhaust was an important source at nominal one-third-octave midband frequencies from 25 Hz to 250 Hz; sound from the air inlet was a significant contributor in the range of midband frequencies from 25 Hz to 500 Hz. Cooling fan noise for the bulldozer was important in the frequency range from 315 Hz to 3150 Hz. For the front-end loader, the enclosed cab in which the operator sits provided good noise reduction at frequencies greater than 400 Hz up to 20 kHz. Examination of the spectrum of the sound produced by these and other heavy earth-moving machines can indicate the need for maintenance efforts to restore noise-control capabilities that were originally installed or which should be installed. © 2005 Institute of Noise Control Engineering.(Institute of Noise Control Engineering, Experimental study of sources of noise from heavy earth-moving machinery) Vardhan, H.; Karmakar, N.C.; Rao, Y.V.2005Item Development of noise spectrum based maintenance guideline for reduction of heavy earth moving machinery noise(2006) Vardhan, H.; Adhikari, G.R.Heavy earth moving machinery (HEMM) is one of the most important sources of noise in open-pit mines. Several studies carried out earlier indicate that noise produced by HEMM can be reduced by proper maintenance. To reduce the overall noise produced by HEMM it is important to identify the components contributing most to the noise. Maintenance of those components can then be carried out rigorously to reduce the noise. This paper presents the development of a maintenance guideline for reduction of HEMM noise based on sound level emissions and noise spectrum studies. The sound level emission and noise spectrum based maintenance guidelines were obtained through noise measurement of HEMM like dumpers, dozers and front-end-loaders over a period of time and under various test conditions. These guidelines can help the maintenance crew for the reduction of noise from HEMM. © 2006 Institute of Noise Control Engineering.Item Feedback active noise control based on transform-domain forward-backward LMS predictor(Springer London, 2014) Pavithra, S.; Narasimhan, S.V.In this paper, a new feedback active noise control (FBANC) system based on the transform-domain forward-backward LMS (TFBLMS) predictor has been proposed. The new ANC system employs the TFBLMS predictor for its main-path (MP) predictor as well as for the noise canceller. To overcome the ill effect of the primary noise field, which acts as an observation noise for the secondary-path (SP) identification, the noise canceller is used. As the main-path predictor is based on the TFBLMS, its convergence rate improves due to its input orthogonalization. Further, its FBLMS nature reduces misadjustment. The use of TFBLMS predictor for noise canceller also gives a good prediction of primary noise at a faster rate, enabling improved SP identification. This improved SP identification indirectly aids the MP predictor to achieve an improved performance. A new filtered-x LMS structure has been proposed to realize the new MP predictor to accommodate the TFBLMS algorithm. The TFBLMS algorithm is applied directly to the noise canceller for SP identification. The proposed new ANC system has been found to have a significantly better noise reduction (by 14.6 dB) over the FBANC system based on tapped delay line time-domain FBLMS algorithm. © 2012 Springer-Verlag London Limited.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