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Steel prices soared in the past years due to the increased demand on the Asian market. Due to difficult economic conditions of the automotive industry it is not possible to transfer expenses to the final customer. Reduction of steel is therefore required to compensate for higher steel prices. Whereas the underbody design space decreases in European vehicles, requirements are getting higher in terms of tailpipe noise and backpressure reduction. This leads to flat structures for mufflers which are integrated into the underbody to achieve as much inner volume for tailpipe noise damping as possible. That requires larger surfaces and results in a rise in costs, weight and radiated noise over surfaces. Additionally, original equipment manufacturers (OEM) require lightweight designs to meet carbon dioxide and consumption targets. Especially for Diesel applications the weight of exhaust systems is penalized by heavy Diesel particle filters.

More and more automobile manufacturers are requiring a typical sound pattern for a car or a platform, even the unique „brand sound” for a whole brand, on the top of their specification. By this image factor sound design becomes increasingly important for the exhaust system development. The whole sound pattern, especially the tailpipe noise of the exhaust system, plays an important role at the subjective impression of the car [1, 2]. There are two sound classifications: the limousines with an harmonic, quiet and discrete sound whereas for sports cars a more rough and powerful sound is requested. Compared with the gasoline engine the diesel engine has, based on inner power driven processes, a minor sound spectrum because its harmonics and main orders are hardly audible and mostly attenuated by a turbo charger. For turbo charged engines special concepts have been worked out in order to achieve a sporty sound.