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. Especially resonances of the connecting pipes and the muffler chambers are used for sound design.
The degree of freedom for sound design is mainly determined by the number and the arrangement of the cylinders. In addition to the number of cylinders a tuning of the valve control timings represents an efficient power driven possibility for a sound design