Effect of non acoustic properties on the sound absorption of polyurethane foams

In this paper the influence of non acoustic properties on the sound absorption coefficient of polyurethane foams as a porous medium is investigated. Biot’s equations with transfer matrix method, as the solution approach are employed to evaluate the sound absorption coefficient of selected polyurethane foams. The major issue is the dependency of non acoustic properties on each other which makes difficulties to examine the effect of parameters individually. Some facts from the results of previous works are used in order to overcome this prominent obstacle. The results show that increasing the porosity doesn’t have a great influence on the sound absorption coefficient and only for highly porous foams, raising porosity decreases the sound absorption performance. The increase of air flow resistivity up to an optimized value, intensifies the absorption capability. Furthermore, for partially reticulated (partially open cell) foams, the increase of tortuosity improves the sound absorption efficiency at lower frequencies.