For long-term customer satisfaction, the aspect of NVH with regard to both interior and exterior noise is one of the major concerns in engine design. Engine components such as oil pans, cylinder head covers, intake and exhaust manifolds, fans and air-control pipes are gaining in importance. Due to its flexible processing and design possibilities, plastic represents a good basic material for complex engine parts. The manufacture of near-field shields, intake systems and mufflers in plastic, for example, not only provides an opportunity for considerable weight reduction but also allows the design of a typical engine sound.
The use of light materials and particularly plastics in car manufacturing has a direct influence on the acoustic response of the parts. The various factors to be taken into account are linked not only with the reduction of the material's mass, but also with its structural stiffness, its geometrical stiffness, its boundary conditions, its sensitivity to duty conditions such as temperature and to the loads applied to the part.
In terms of efficiency and costs, double-wall systems are an interesting alternative to classical absorption materials (such as foams) or heavy layers, but the sensitivity of these systems must be taken into consideration in the design of the part or system to be insulated. Depending on their location or function, certain parts are much better suited to the integration of these techniques than others.