Sound-absorbing porous materials: a review on polyurethane-based foams

In recent years, noise pollution has become one of the most critical human environmental problems. It has adverse effects on people’s health and their work efficiency. Therefore, porous materials have gained enormous attention because they offer excellent sound absorption properties, low density, high specific strength, etc. In this review article, sound absorption in materials with specifically related properties such as sound absorption coefficient, sound absorption mechanisms, and types of metallic and non-metallic sound-absorbing foams are studied and discussed. Moreover, various kinds of porous polymeric materials are summarized, and in this respect polyurethane (PU) composite foams are represented with more details. Polyurethanes have several advantages such as reasonable physical, mechanical and thermal properties, acceptable processability, and chemical resistance. Polyurethane foam is a polymeric material with a cellular structure which makes it an effective sound absorber. Furthermore, various methods of preparing polymer foams are also presented. Different nanoparticles, synthetic and natural fibers are added to PU foam to enhance its acoustic properties. These additives and their effects on the sound absorption properties of PU foams are listed. Besides, various polymeric foam formation methods are explained with their advantages and disadvantages. Finally, discussion covers “porosity” as one of the most important factors on sound absorption properties of materials. Graphical abstract