Generalized Light-Weight Concepts: Improving the Acoustic Performance of Less than 2500 g/m2 Insulators 2009-01-2136

The weight reduction challenge has taken a new shape in the past two years due to high pressure on CO2 emissions in the automotive industry. The new question is: what level of acoustic performance can you get with an insulator weighting less than 2500 g/m²? The existing solutions at this weight being mainly dissipative (absorption) concepts give a satisfactory performance only if the pass-throughs are poor and present critical leakages.

Respecting the less than 2500 g/m² weight target, we have developed a wide range of new or optimized concepts switching from extremely absorbing to highly insulating noise treatments playing with multi-layers insulators (typically three to four layers), in combination or not with tunable absorbers on the other side of the metal sheet (in the engine compartment for example). Each system answers a specific pass-through quality situation, the best concepts combining broadband absorption with good insulation slopes, which oblige to develop very light airflow resistive non-wovens and light airtight barriers in parallel to optimized poroelastic materials like foams or felts.

This paper illustrates various applications of these Generalized Light-Weight Concepts with and without the influence of pass-throughs and intermediate cavities like instrument panels, modelized and optimized using poroelastic finite elements and correlated with measurements. This approach shows with efficiency that optimizing a noise treatment without its environment may be misleading.