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To meet the legal requirements concerning noise emission of vehicles, ERAS GmbH and Arvin- Meritor Emissionstechnologies GmbH have established a co-operation regarding the development of an active noise control (ANC) system for car exhaust systems.
Besides the acoustical benefits the most important advantage of an active system is that the mufflers can be built smaller and lighter. Moreover, these systems have the potential for very specific sound design in an effective way.
The ANC system controls the emitted noise at the orifice by an additional anti noise source inside the exhaust pipe. This source is realized by a dynamically driven flap in the cold end of the exhaust system. The static aperture angle and the dynamic angle are controlled with respect to the load and the revolution of the engine. The actuator system consists of the flap, an axle with bending elements and a motor. Due to the integration in the exhaust pipe the actuator system has to withstand very high thermal loads.
In the present paper the main requirements on measures for noise reduction and sound design in car exhaust systems are described. The concept of the ANC system is presented. The main technical characteristics of the actuator system and the control strategy are explained. The operability of the system is demonstrated on the basis of investigations on an engine test stand. The acoustical behavior of an exhaust system with integrated ANC system is compared to a current production exhaust system.