In today's world, automotive manufacturers are required to decrease CO2 emissions and increase the fuel economy while assuring driver comfort and safety. To achieve desired acoustic performance targets, automotive manufacturers use various Noise-Vibration-Harshness (NVH) materials which they apply to the vehicle Body-In-White structures either in the body or paint shop.
Beside the sound deadening coatings applied onto the underbody of vehicles, they have historically used either constrained or free-layer sheets. The majority of these damping pads/sheets, so called asphalt sheets, are applied onto the floor pan inside the vehicle. These pre-manufactured and vehicle specific die-cut sheets are typically highly metal-carbonate, sulfate or silicate filled asphalt systems with a high specific gravity. Depending on the size of vehicle, the amount of these sheets can reach application weights of 10∼20 kg/vehicle.
This paper will document the technical path that Dr. H. Oberst1 laid with his fundamentals for free layer damping from bending vibration studies and how application of the Oberst equation has led Henkel to develop 1st, 2nd and 3rd generation Liquid-Applied Sound Damping materials (LASD) using the parameters in the equation with the goal to achieve better NVH management and lower weight per vehicle.