Computational Prediction and Measurement of Break-out Noise of Mufflers

A typical simple expansion chamber muffler has been analyzed for its transverse transmission loss performance using Finite Element and Boundary Element methods, considering the fluid-structure coupling for a given acoustic excitation. The resulting break-out noise from the muffler shell together with the end plates, and the transverse transmission loss have been predicted. The incident sound power on the ‘muffler proper’ has been measured making use of the two-microphone technique and the radiated sound power from the muffler shell together with the end plates has been obtained through Sound Intensity (SI) measurements around the muffler. The computational predictions and the experimental results are in reasonable agreement. Finally, parametric studies have been presented using numerical tools, shape and thickness of the muffler shell and end plates as parameters, as an aid to the muffler design process.