In recent years, due to the increasing urbanization and development of industries, noise pollution has become a major challenge. This has led to increased public awareness and strict government regulations on noise and pollution control. One of the most important ways to reduce noise pollution is the use of acoustic absorbers. Nonwoven fabrics are known as the most important acoustic absorbers due to their porous and bulky interior structure. The main problem of these materials is low noise absorption at low frequencies. For this reason, increasing noise absorption at low frequencies has always been a challenge for researchers. Increasing the flow resistivity is one of the ways to increase sound absorption at low frequencies. In recent years, the use of nanofibers coatings on nonwoven fabrics to increase the flow resistivity and consequently increase the absorption at low frequencies has been reported by some researchers. Despite improved sound absorption, these structures have limited sound absorption at low frequencies. Hollow nanofibers will increase the flow resistivity due to the higher surface area to volume ratio. For this purpose, in this study, we investigated the acoustic properties of hollow nanofibers. For this purpose, in the present study, core-shell nanofibers were first produced by using polyacrylonitrile and polyvinyl acetate polymers via coaxial electrospinning. Then, by removing the core material, hollow nanofibers were prepared. Nonwoven fabric was also produced using a laboratory setup. Then, the acoustic properties of the specimens were investigated by placing the core-shell and hollow nanofibers on and behind the nonwoven fabric. The results showed that the nonwoven fabric has a sound absorption of the type of viscosity absorption. Placing nanofibers on the back of nonwoven fabric increased sound absorption at all frequencies. In fact, when the nanofibrous web is placed behind the nonwoven, with increasing the thickness of the web, the absorption of sound increases due to the increased flow resistivity. In the case of nanofibrous webs containing hollow nanofibers it is observed that in addition to increasing the sound absorption coefficient with increasing thickness, the peak of sound absorption shifts from about 1000 Hz for the web produced for 4 h to about 630 Hz for the web produced for 8 h. In the second case, the results showed that placing nanofibers on the nonwoven fabric changes the absorption mechanism from viscosity to resonance type. It was observed that by placing the core-shell web of nanofibers on the nonwoven fabric and increasing the thickness of the these nanofibers, the peak of absorption occurs for thickness of 17 ?m at 1250 Hz, for 28 ?m at 1000 Hz, and for 37 ?m at 800 Hz. Also, by placing hollow nanofibers on nonwoven fabric and increasing the thickness of nanofibers the peak is observed for thickness of 17 ?m at 800 Hz, for 28 ?m at 630 Hz and for 37 ?m at 500 Hz. According to the results, when the nanofibers are placed on the back of the nonwoven, the thickness of the layer increases as the NRC increases. In addition, hollow nanofibers in each case have higher NRCs than nonwoven fabrics and core-shell nanofibers.