Abstract
This work examines the absorption characteristics of two well-known porous materials-polyurethane foam (PUF) and polystyrene foam (PSF)-both of which are locally produced and readily available in Saudi Arabia. Nine samples were selected after a careful investigation of the local markets. The chosen samples were systematically tested in conformance with the ISO 354 and ISO 9613-1 standards in the reverberation chamber. The samples were subjected to three sets of measurements. The first set of measurements was obtained with the samples installed directly against the chamber wall (DOW, Type A mounting). For the second and third sets of measurements, the samples to be tested were installed with an air gap of 50 and 100 mm from the wall using wooden joists of 50 x 50 and 50 x 100 mm, respectively. Results showed that polyurethane foam is an efficient absorber, whereas polystyrene is not. It was also observed that sound absorption improves remarkably in the low-frequency range by increasing the air gap between the tested sample and the solid wall behind it, but this improvement becomes very limited in the mid- and high-frequency range. Adding a polystyrene and/or CF13 layer under the tested material generally improves the absorption characteristics when compared with the case where the material is installed directly against the wall or floor. Nevertheless, the best performance is achieved when the material is installed at least 50 mm from the wall or floor. Furthermore, results showed that the thickness of the material has a stronger effect on the absorption than the density in terms of the "correlation coefficient". The other factors that affect the sound absorption include air flow resistivity, air permeability, and the microstructure of the tested samples.