AbstractIt was confirmed that one of the principal factors which influences the acoustical absorption of flexible polyurethane foam is flow resistance of foam. Normal polyester‐based flexible polyurethane foam itself has an adequate value of flow resistance and shows fairly good sound absorption. Acoustical absorption of normal polyether‐based flexible polyurethane foam, which generally has lower flow resistance, can be improved by using some expedients such as setting up a certain skin layer on the foam surface so that the flow resistance of the foam can be increased. Surface treatment of foam such as gluing film, heat melting, spraying, or heat adhesion with film can not only improve sound absorption and mechanical properties of polyether‐based flexible polyurethane foam, but also improve the hydrolysis resistance of polyester‐based flexible polyurethane foam. Inserting some metal foil or plastic film between flexible polyurethane foams can change the sound absorption behavior according to the position of the foil or the film in the foam. The effects of foam thickness, existence of air layer behind foam, and foam profiling on acoustic absorption were also inves
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