The impact of pass-by noise legislation on the design of exhaust systems

Authors

Jan Krüger, Peter Wink, Maike Werner, Eberspächer Exhaust Technology GmbH & Co. KG

Year

2019

Summary

In all major markets, the legislation on emissions (CO₂, NOx, and PM) has been changed drastically and limit values have been lowered over the last years and will be even lower in the near future. Moreover, the new pass-by noise rules require more testing e.g. for additional sound emissions provisions (ASEP) and limit values are more stringent than ever according to R51.03, particularly with the phase coming into force in 2024. Besides the tire noise, the powertrain and here in  particular the exhaust tailpipe noise is nowadays the main contributor to pass-by noise. This will have an enormous impact on the design of future passenger cars, their powertrains, and finally their exhaust systems with an inherent cost penalty as e.g. muffler systems need to be larger or more complex to emit even lower noise.
The technology for Active Noise Cancellation has been investigated in the automotive industry for many years. The basic principles are well understood and active engine mounts as well as in-cabin active noise cancellation have been in series production for a few years. For exhaust muffler systems, several studies at prototype level have demonstrated technical feasibility and resulted in substantial benefits for acoustical performance and sound design. Moreover, advantages in package space, weight, and backpressure have been demonstrated for different engine set-ups. In this publication, active exhaust systems will be compared to conventional cold-end systems. Their
main advantages in acoustics, weight, and package space under different scenarios will be analyzed.

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