Todays legislative requirements - particularly in Europe and Japan - already demand low noise vehicle powertrains. For engine designs now on the market which do not meet the required noise levels, vehicle manufacturers have to rely mainly on additional shielding to meet these demands. To achieve even lower legislated noise levels, as in force in certain European countries, these vehicles are now equipped with almost full engine enclosures.
Shielding and enclosures have been proven to be effective for vehicle noise control (1*,2,3,4) but are regarded by vehicle manufactures as additional parts with disadvantages in terms of cost and accessability for maintenance. In relation to the most stringent vehicle noise legislation in Europe, there is little further potential for acoustic improvement of the vehicles when they are equipped with enclosures and most current types of engine. Therefore, to meet more stringent noise requirements, new engines entering the market will have to incorporate all feasible noise reduction techniques in their design.
In this paper, features necessary for the design of low noise engine concepts, will be discussed. It will also be shown that the required noise targets can be achieved when considering engine performance, reliability, cost and future emission regulations.