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SEA models are used to predict the performance of acoustic packages when assessing the performance of vehicle level or body noise reduction targets. One of the challenges faced by CAE engineers is the ability to estimate the performance of different materials used in the sound package at the design stage. Analysts can use measured data in the form of insertion loss and random incidence absorption if available or can predict the performance of materials using a Biot type description. The use of the full poro-elastic Biot model for materials requires knowledge of the fluid and elastic properties, however a limp or rigid model can be used to describe the material based only on the fluid properties and this is often sufficient to describe fibrous materials. In this paper a method will be outlined which will allow the material properties of fibrous materials to be estimated from basic normal incidence data that is provided by material suppliers.

There are many software tools in use today that are implementing the Biot, or complementary, method for the evaluation of foam and fiber materials. The justification of this process is to understand which mechanisms of the noise control material are contributing to the noise reduction and to optimize the material based on its acoustic properties. The disadvantage of this method is that it is quite complex and time consuming to test a material in order to extract the underlying properties that govern the acoustic performance. An alternative inverse method for material characterization based on simple impedance tube measurements has been developed lately. This paper recalls the physics and mathematics behind the method and concentrates on its validation.

Porous materials have been applied increasingly for absorbing noise energy and improving the acoustic performance. Different models have been proposed to predict the performance of these materials, and much progress has been achieved. However, most of the foregoing researches have been conducted on a single layer of porous material. In real application, porous materials are usually combined with other kinds of materials to compose a multilayered noise control treatment. This paper investigates the acoustic performance of such treatments with a combination of porous and non-porous media. Results from numerical simulation are compared to experimental measurements. Transfer matrix method is adopted to simulate the insertion loss and absorption associated with three samples of a noise control treatment product, which has two porous layers bonded by an impervious screen.