Drastic exterior noise reduction through optimization of acoustic shielding package

In the context of the upcoming reduction of Pass-By-Noise limits in the EU regulations, automotive manufacturers need to implement new concepts of shielding package. ECOBEX is a French funded research project aiming at reducing the powertrain noise contribution of the vehicle by 5 to 7 dBA, whilst restricting additional mass and cost. Bringing together OEM, raw materials suppliers, shielding manufacturers, universities and specialized consultants in this research program enabled innovations in materials, design, tests and computational methods. This paper will focus on a new procedure for the optimization of the shielding package, based on a precise 3D localization and quantification of the acoustic sources of the powertrain and on their implementation in an Energy Boundary Element model, computing the acoustic propagation. Intensity maps emphasized the dominant acoustic paths and highlighted mitigation opportunities in terms of absorption and insulation. The shielding efficiency could then be optimized with an improved accuracy, taking into account the spatial and frequency characteristics of both source and shielding. Materials were chosen to match local absorption and insulation optimums regarding their noise exposure spectra, whilst coping with all industrial constraints. Measured and computed results are encouraging, and the optimized shielding package is shown.