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. This approach will then allow the effect of compression on the material properties to be predicted and the impact on the acoustic performance to be estimated. In addition it will allow the analyst to estimate the effects of increasing or reducing the fiber weight. Predictions will be compared with measured data.