Application of Micro-Perforated Composite Acoustic Material to a Vehicle Dash Mat

In recent years several variants of lightweight multi-layered acoustic treatments have been used successfully in vehicles to replace conventional barrier-decoupler interior dash mats. The principle involved is to utilize increased acoustic absorption to offset the decrease in insertion loss from the reduced mass such that equivalent vehicle level performance can be achieved. Typical dual density fibrous constructions consist of a relatively dense cap layer on top of a lofted layer. The density and flow resistivity of these layers are tuned to optimize a balance of insertion loss and absorption performance. Generally these have been found to be very effective with the exception of dash mats with very high insertion loss requirements. This paper describes an alternative treatment which consists of a micro-perforated film top layer and fibrous decoupler layer. Prototype dash mats were constructed after performing Statistical Energy Analysis (SEA) vehicle level assessments of constructions using flat stock insertion loss and absorption data. Vehicle level test results are presented showing that the micro-perforated systems are capable of competing with dual density lightweight systems, and also have potential to be enhanced to provide vehicle level performance equivalent to heavier barrier-decoupler systems at less mass.