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The noise treatments weight reduction strategy, which consists in combining broadband absorption and insulation acoustic properties in order to reduce the weight of barriers, depends strongly on surface to volume ratio of the absorbing layers in the reception cavity. Indeed, lightweight technologies like the now classical Absorber /Barrier /Absorber layup are extremely efficient behind the Instrument Panel of a vehicle, but most of the time disappointing when applied as floor insulator behind the carpet. This work aims at showing that a minimum of 20 mm equivalent “shoddy” standard cotton felt absorption is requested for a floor carpet insulator, in order to be able to reduce the weight of barriers. This means that a pure absorbing system that would destroy completely the insulation properties and slopes can only work, if the noise sources are extremely low in this specific area, which is seldom the case even at the rear footwells location.

Polyurethane foam (PU foam) is widely used in automotive noise reduction palliatives. As a decoupling insulator its acoustic performance depends on intrinsic properties, called “Biot” parameters. An important decoupling parameter is the apparent stiffness of the PU foam cell structure, as this controls the transportation of vibrational energy, with “softer PU foam” being the preferred option. However, some areas of application, for example in automotive carpet design, requires stiffer PU foam in order to accommodate under foot comfort. For a comprehensive approach to automotive component design, it is necessary to calculate the appropriate spatial PU foam properties ideally without the need for series of prototypes. This paper describes the methods and processes used when compiling and validating a material database capable of predicting the acoustic performance of flat sample or spatially complex 3D component with minimal prototype manufacture.

Significant advances have been made over the last 15 years in the field of modelling the acoustic properties of foams from the description of their microstructures. It entails a multidisciplinary work at the junction between physico-chemistry and mechanics of porous media, which involves a dialogue between different disciplines and requires the joint development of several techniques (imaging, upscaling, numerical computations, and experimental identification). It seems to be of timely interest to take stock of the methodological developments that have provided guidance on how to manufacture the new generation of foams with enhanced properties and to identify possible future methodological developments.