The effect of cellular structure in the flexible polyurethane foams on the sound absorption behavior is investigated for improved sound environment within vehicles. Two types of gelling catalyst and water are used for producing well-defined cavity and pore structure in the foams. The catalyst, having high activity in urethane reaction, produces a larger number of small cavities and pores in the foams compared to the catalyst having low activity. A high number of small cavities can also be obtained at high water content from the restraint of neighboring cavities due to actively formed urethane matrix. The foam density decreases with increasing water and catalyst contents. Sound absorption efficiency is usually low at low foam density, but the results show improved sound absorption efficiency even at the reduced foam density because of the high number of well dispersed small cells in the foams. Display omitted •Flexible polyurethane foams for sound absorption materials•Sound absorbing ability of well-designed cellular structured foams•High number of small cells for high sound absorbing ability•Use of a strong gelling catalyst for high number of small cells