Lightweight Design for Fibrous acoustic package of automotive

Carpet is an important acoustic part. Carpet plays key role on reducing engine noise, road noise and even exhaust noise. Fibrous type of carpet is one choice for saving weight. When using it, many problems arise. First is how to balance the sound insulation and sound absorption, to achieve better cabin noise reduction. Second is, in low frequency, structure-borne noise occurs because of weight reduction and damping reduction. Third question, carpet insulator covers many zones, such as toepan of firewall, floor, rear seat and even trunk floor, so engine noise, road noise, exhaust noise must be controlled by carpet. Different sources have different characteristics and different noise level, so design the acoustic treatment lay-ups of carpet in different zones becomes important. To solve structure-borne noise below 300Hz, damping effect of carpet insulator was studied with FEM tool, and relation between damping loss factor and bending and compression stiffness was declared. It can solve the structure borne noise when fibrous carpet is used. To solve third question, optimized lay-ups was input into SEA software to calculate the interior noise of multiple loadcase such as engine noise and road noise, hybrid lay-ups of carpet was finalized after iteration.