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ABSTRACT The main aim of this study was to investigate the usability of polyurethane (PU) and polyacrylonitrile (PAN) nanofibers for improving the sound absorption of conventional polyester nonwovens in wide band of frequencies along with weight and thickness reduction. The effect of nanofiber and nonwoven layers number, nanofiber layers surface density, and the type of nanofiber polymer on the sound absorption was studied. To find the optimum conditions for achieving high sound absorption, response surface methodology was used. The results showed that the sound absorption of composite samples is improved when the nanofiber layer number or its surface density increased. The results also showed that the sound absorption of composites is enhanced by using PAN instead of PU. At a constant surface density, the higher resonant peak, without shifting, was achieved with increasing the nanofiber layers number. Optimization process showed that samples containing PAN nanofiber layers with surface density of 4.72 g/m2 and six nonwoven layers have highest average sound absorption coefficient. [ABSTRACT FROM AUTHOR]