© 2018 JETIR December 2018, Volume 5, Issue 12 www.jetir.org (ISSN-2349-5162) JETIRDZ06133 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org 1022 PREDICTION OF TRANSMISSION LOSS ON A SIMPLE EXPANSION CHAMBER MUFFLER Ujjal Kalita * , Dr. Manpreet Singh School of Mechanical Engg., Lovely Professional University, Phagwara, Punjab, India. Abstract: Over a few decades it is observed that the number of vehicles has increased because of which the level of noise emitted by vehicles is getting worse. Exhaust noise is preferred to be highest than the other structural noise. So, acoustic filters are used for reducing this noise coming from the exhaust system. Simple expansion chamber muffler is one such filters. Transmission loss is the main performance parameter for evaluating the noise reduced by this muffler. In this study a new design of muffler is proposed by optimization, where length and diameter of chamber are considered as the main parameter for optimization. This design is created in CAD software and the acoustic analysis for the muffler is performed through simulation method in ANSYS software. The results obtained from analysis are compared with the work performed by two other authors. From this it is found that the optimized single expansion chamber muffler gives us better acoustic performance value. Keywords: Simple Expansion chamber, Muffler, Transmission loss, Noise reduction. 1. Introduction Over the last two decades number of vehicles has increased, due to which the level of noise emitted by vehicles is getting worse. In this exhaust system produces noise almost ten times than that of structural noise. So special attention has been paid on exhaust system by using acoustic filters. Muffler is one such type of acoustic filter which plays an important role in reducing exhaust noise. That’s why many researchers have selected muffler as their prime area of interest for research. In general, the inlet pressure and outlet pressure of muffler are taken into consideration because the mufflers performance parameters entirely depend on it. A vast number of simulation methods are available to design and check its performance virtually. In earlier years due to the lack of advancement in computer use and functions there has been limitations for predicting mufflers performance and its properties cannot be aligned with practical results sometimes. But with the invention of more sophisticated simulation software and solvers like Finite Element Method (FEM) and Computational Fluid Dynamics (CFD), it has become easy for predicting this muffler performance with great accuracy [1]. A muffler or silencer is an acoustic filter applied at exhaust system for reducing the emitted noise of an IC engine. In most internal combustion engines, compressors, air conditioning system etc. mufflers are installed within the exhaust system. The muffler is used as an acoustic soundproofing device for the reduction of the noise emitted by the exhaust system by way the way of acoustic quieting. In most internal combustion engines, compressors, air conditioning system etc. mufflers are installed within the exhaust system. The muffler is used as an acoustic soundproofing instrument for the noise reduction at the exhaust system by the way of acoustic quieting [7]. In automotive industry, reactive muffler or dissipative mufflers are normally used and they work at certain frequency spectrum. Reactive mufflers are favorable at low frequency ranges whereas dissipative are favorable for high frequency ranges about 1500-2000 Hz [9]. The science of acoustics of muffler and ducts is over 150 years old. Davis et.al in 1954 had done the first comprehensive experiment on the design and analysis of muffler. Davis et al. used the acoustic transfer matrix method and studied the noise reduction principle of muffler. Experimental verification is also performed and with respect to it muffler research theory is established [2]. In their report they had done experiment on 77 different single chamber and multiple chamber mufflers. From the experiment they have plotted the attenuation to frequency curve and this result were compared to the theoretical results. Later Fukuda et al. had developed the transfer matrix method (TMM) which is ideally suited for acoustical modelling of cascaded element in automotive mufflers [3]. This strategy made the standing wave