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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.

Cabin acoustic comfort is a major contributor to the potential sales success of new aircraft, cars, trucks, and trains. Recent design challenges have included the increased use of composites, and the switch to electrically powered vehicles, each of which change the interior noise spectral content and level. The role of acoustic absorption in cabins is key to the optimisation of cabin acoustic comfort for modern vehicles, with acoustic impedance data needed in order to assess and optimise the impact of each component of a given lay-up. Measurements of absorbing interior trim are traditionally performed using either sample holder tests in a static impedance tube (impedance and absorption), or through tests in reverberation rooms (absorption only). Both of these procedures present challenges. In-tube absorption and impedance measurements are destructive, requiring highly accurate sample cutting and sealing.