Noise legislation and subjective customer demands set future standards for noise and vibration control in all types of vehicles, from small passenger cars to heavy trucks. To obtain the required improvements, it is necessary - particularly for vehicles with diesel engines - to deal with all parameters which effect vehicle interior and exterior noise.
For optimisation of total vehicle noise-vibration-harshness (NVH) the interaction of the power unit and other noise sources with the power unit mounting system, the vehicle chassis structural response and the vehicle local transmission losses have to be taken into account. It is then possible to design appropriate measures not only to meet certain noise levels, but most importantly to achieve, in parallel, a high quality subjective interior noise character over the complete operating range.
In this paper the procedure adopted for optimising the NVH of a production off-road vehicle equipped with a DI-TCI diesel engine will be reported. The short time scale available for the engine and vehicle project demanded the adoption of a refined strategy which allowed, in parallel, both a low overall noise level and a high quality noise character to be achieved by feasible and cost effective methods.
This combined approach, adapted for balancing and controlling engine noise, other vehicle noise sources and vehicle response with respect to exterior and interior noise and subjective noise character, will be discussed.