Acoustical properties of novel sound absorbers made from recycled granulates

The paper begins with a discussion of materials made using recycled granulates. The macroscopic properties (e.g. flow resistivity, porosity, tortuosity, etc.) that control the acoustical behaviour of these materials are then defined as are methods for their measurements. The acoustical characterisation of porous media is considered next, followed by discussion of the acoustic performance of the materials. The characteristics of these novel materials are illustrated through experimental and theoretical models involving sound absorption and transmission.