In the automotive industry, it is common to have different departments designing different parts of the floor. The NVH department may define the overall structural stiffness and might request beading to be added to specific panels to reduce the vibration response locally. It may also request damping pads to be added on the remaining vibration hot spots of the floor. The acoustic group then needs to define the acoustic trim needed to meet the vehicle targets based on the constraints prescribed by the NVH department choices concerning structural stiffness, floor construction, beading, damping pads… In many cases, the NVH and acoustic groups are not communicating and some solutions proposed by one group are detrimental to the other group. For example, it has been shown that contrary to popular belief, adding beads to a structure can actually reduce noise at the first few modes of a plate while significantly increase noise radiation at higher frequency. This paper presents an investigation of how the structure, the beading, the damping pads and acoustic trim can be integrated into a holistic design process to evaluate the effect of all these components on the floor vibration and sound pressure level (SPL) inside a vehicle. In this study only a floor panel is studied to isolate phenomena. A vehicle cavity with seats and appropriate damping is used to represent the interior of the vehicle. The floor structure, beading, damping pads, acoustic trim and acoustic cavity are modelled using finite elements (FEM). Biot parameters are used to represent the poro-elastic layer physical properties. Different configurations including classical steel and innovative composite laminated panels are compared and associated with different types of beading, damping treatments and acoustic trim to evaluate the effect of the full floor component on the vibration response of the floor and most importantly the SPL at the driver’s ear.
2011 – AAC – Aachen Acoustic Colloquium, Aachen, Germany
Denis Blanchet (ESI Group, Germany)
Arnaud Caillet (ESI Group, Germany)