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Reducing noise emissions from vibrating components in a vehicle's underhood environment has always been a priority at the OEM level. In recent years, it has been receiving a rather significant amount of attention due to the increased usage of plastics in the underhood environment. Due to it's lower mass density property (as compared to metallic materials), plastics have some general disadvantages in terms of acoustical insulating properties. Yet, the design of these parts can be changed so that the noise emissions from plastic components can be reduced to levels similar to metallic components by using advanced simulation techniques and optimizing the vibro-acoustical behavior of the part. The goal of the design engineer has changed from only traditional part design and structural or weight optimization to include acoustical optimization of the plastic underhood component.

Noise Attenuation for Polyamide Intake Manifolds Since the stiffness of polyamide is lower than aluminum, special techniques have been developed to increase local and global stiffnesses of polyamide intake manifolds. The increased stiffness results in parts with noise emissions equal to or less than equivalent aluminum intake manifolds with twice the wall thickness. These special techniques enable engineers not only to attenuate noise, but to “tune” the remaining noise emissions for a desirable sound quality.