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In current automotive research, increasing attention is being paid to the design of mufflers due to the lower noise levels which have been established by the acoustic international standards. The traditional design approaches are no longer sufficient to meet the standards and more refined techniques are necessary. Within this context, a specific test rig was built at the Energy Engineering Department of the University of Florence to analyze the acoustic characteristics of both industrial mufflers and simplified models. In particular, the latter is commonly used to investigate in detail the physical phenomena connected to the acoustic response of these disposals and to calibrate numerical models. The test rig operates at ambient condition with no flow.

Increasing interest is being paid to noise pollution of internal combustion engines and as a result, recent international standards imposed more severe limitations to acoustic emissions on engine manufacturers. In particular, the noise coming from gas-dynamic interactions has an important influence in determining the final noise level of the engine; as a consequence, the muffler design is currently being considered as one of the most important research threads for engine companies. Within this context, the 1D approach to numerical simulations, which has been successfully applied by industrial designers to the fluid-dynamic design of the engine, is considered to be inaccurate in the evaluation of the acoustic behavior of the muffler for medium-high frequencies. On the other hand, an extension of the applicability of these codes in the medium-high frequencies would be desirable.