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In this paper, sound transmission characteristics of typical stamped steel automotive body panels are investigated. In particular, focus was placed on the dash panel since it separates the interior space from the engine. Three dash panels were considered with the same geometry but different damping characteristics. These dash panels included a bare steel dash, a bare steel dash with a Patch Constrained Layer (PCL) and a laminated steel dash. Sound transmission loss was measured in a transmission loss suite. It was observed that the measured transmission loss of the laminated steel dash was significantly higher than the other dash panels throughout the mid and high frequency regions. A hybrid approach using both Finite Element Analysis and Statistical Energy Analysis (SEA) was used to predict and correlate the sound transmission loss for these panels. The geometry effects of the dash panels were considered while calculating SEA parameters.

Structure borne sound is one of the most important reasons of noise pollution in the automobiles and aircraft's. Noise is mostly generated by the vibrating panels excited by either a mechanical or an acoustical excitation. Examples of the typical vibrating structures in automobiles are engine cylinder, gearbox cover, transmission system covers, panels of the body etc. Sound radiation characteristics are also important in the phenomenon of resonant sound transmission through a panel. Resonant sound transmission occurs because of resonant modes of the panel within the frequency bandwidth of interest. Typical example of resonant sound transmission is the transmission through a firewall of an automobile, which forms the partition between the engine compartment and the cabin interior. Radiation characteristics can be typically defined by radiated sound power, radiation efficiency and space average mean square velocity of the panel.

Three dimensional finite element analysis of mufflers has been carried out using ANSYS general purpose program. Analysis of simple expansion chamber muffler, extended tube muffler, tapered chamber muffler, offset chamber muffler and flow reversing chamber muffler has been carried out to predict the transmission loss. This three dimensional FEA technique has proved to be successful for the analysis of geometrically complicated mufflers where one dimensional theories can not be used. Parametric analysis of a simple expansion chamber muffler has been carried out to study the effect of expansion ratio, expansion chamber length, number of partitions within a chamber and unequal partitions. Analysis of acoustic cavity of a simple expansion chamber muffler has also been carried out to predict the natural frequencies and acoustic mode shapes.