On Theoretical of Transmission Loss in Exhaust Muffler System

Abstract

Exhaust muffler system iscommonly used to reduce noise associated with internal combustion engine exhausts.This paper presents a numerical analysis of transmission loss for exhaust muffler by using transfer matrix method. The objective of this study is to develop the computer program to predict the transmission loss of muffler.The influence of cross sectional area of pipe, effect of muffler length and temperature towards the transmission loss of muffler is discussed as well in present study. The efficiency and capabilities of the computing transmission loss is compared to the experiment results obtained from the previous established research paper.

Analysis of Baffle Effect for Measuring Transmission Loss

“…This theory is also used by H. Abdullah et al [1] to find the transmission loss. By considering the sound transmission in a layer of acoustic medium of finite length (L) as shown in Fig.…”

“…Expansion chamber is used for transmission loss comparison between the numerical and experiment of the muffler. The physical geometry of the expansion chamber is as following the diameter of the inlet and the outlet muffler are the same, which is 34.9 mm; the diameter of muffler chamber is 153.2 mm and the length of muffler is 203.2 mm [1]. Fig.…”

“…Exhaust noise from engines is one of the noise pollution to the environment. Nowadays with the increase of population density, the increasing of exhaust noise is also caused by the increasing of the vehicle on the road [1]. Most of the engine exhaust noise in car is due to the discharge noise from the tailpipe opening and the shell noise.…”

“…This method has been used for previous research to find the transmission loss [1]. Through the research the author found that effect of cross sectional area increase the transmission loss meanwhile analysis of muffler length and temperature does not contribute significant effect of the transmission loss.…”

Muffler structure improvement based on acoustic finite element analysis

“…This method could predict the muffler acoustic characteristics quickly and accurately. Abdullah et al 10 used transfer matrix method combined with computer programming to predict the transmission loss of the muffler and verified the analysis results by experiments, and the result showed that the muffler's expansion ratio increases, the acoustic attenuation performance would increase in the low-frequency band below 1000 Hz as well. Mimani and Munjal 11 used a 3-D semi-analytical method employing a uniform piston-driven model and Green's function technique to analyze a hollow elliptical chamber muffler with an end inlet and a side outlet.…”