Measured anisotropic air flow resistivity and sound attenuation of glass wool

The air flow resistivity of glass wool has been measured in different directions. The glass wool was delivered from the manufacturer as slabs measuring 100x600x900 mm3, where the surface 600x900 mm2 was parallel with the conveyor belt used in the manufacturing. Directions in the glass wool are described by a coordinate system with the X axis perpendicular to the conveyor belt, the Z axis in the direction the conveyor belt moves, and the Y axis perpendicular to the two other axes. It was found that the resistivities in the Y and Z directions were equal in all cases. For density 14 kg/m3 the mean resistivity in the X direction was 5.88 kPa s m(-2) and in the Y direction 2.94 kPa s m(-2). For density 30 kg/m3 the mean resistivity in the X direction was 15.5 kPa s m(-2) and in the Y direction 7.75 kPa s m(-2). A formula for prediction of resistivity for other densities is given. By comparing measured values of sound attenuation with results calculated from resistivity data, it is demonstrated that the measured attenuation can be predicted in a simple manner.