Some Strategies to Meet Future Noise Regulations for Truck Engines

Future noise regulations for trucks require a 1 m engine noise level of 95 dBA or below at rated speed and load. To achieve this goal, noise reductions at source - lowering the excitation forces and the structure response - or secondary measures such as engine mounted shielding or encapsulation have proved to be effective. Since encapsulation technology is already well advanced, although rarely applied by vehicle manufacturers, the reduction of noise at source has become an important technique. In this paper it will be reported that the required noise level of 95 dBA can be achieved by the combined effect of reducing combustion excitation, optimising the engine structural response and using low noise materials for noisy engine parts. For all three subjects different approaches for noise reduction and their effect on overall engine noise, performance and reliability will be discussed in detail.