In a developing and increasing world, the increment in the consumption of natural resources brings environmental problems together. The use of plant raw materials has great importance in the construction industry, which has a high consumption rate. Increasing demand to develop sustainable and environmentally friendly materials has increased the use of natural fibers in sustainable building materials (sound absorption, heat and sound insulation). The fact that hemp fiber does not have high water consumption in the production, can be grown without the need for fertilizers and pesticides, as well as leaving a rich soil structure for the next crop by destroying weeds ensures the protection of the soil and the environment. From this point of view, in this study sound insulation properties of hemp fiber reinforced composites were investigated. Polypropylene fiber was used as a matrix material. To compare the performance of hemp fiber, cotton fiber was also utilized and different constructions were produced from these materials. The composites were produced by the hot-press method. It was found that the composites made of hemp fiber showed significantly higher sound insulation than the cotton fiber reinforced composites and can be used as a sound isolation material at specific high frequencies.