Sisal fiber (SF) and waterborne polyurethane adhesive were used to prepare SF‐based sound absorption material through hot press molding. SF with elastic polyethylene (PE) film interlayers was also fabricated as a new type of sound absorbing composite. The effects of SF treatment methods and PE film on sound absorption coefficient were evaluated. The alkaline‐treated SF composite had higher sound absorption as compared with the untreated SF composite when the sound wave was below 5500 Hz. The sound absorption peak of alkaline/oxidation‐treated SF composite moved towards low‐ and middle‐frequency regions. The SF/PE film composite showed that at low‐frequency the more layers of PE film inserted the better sound absorption property. The mass‐temperature relationship and FTIR of the composites were discussed. The SF surface and the cross section of the composites were observed by SEM, which showed the void structure and microfiber contributed to enhancing sound absorbing property. POLYM. COMPOS., 39:2812–2818, 2018. © 2016 Society of Plastics Engineers