Operators of agricultural machines are exposed to an extensive range of indirect vibrations through the seat, which gradually causes chronic damages. One of the ways to reduce the vibrations imposed on the operators is to use appropriate materials in tractor seat cushion. In this regard, the present study was carried out in order to select appropriate foam and investigate different factors in reducing vibrations imposed on tractor operator’s body so as to promote his health and enhance his efficiency. Therefore, varieties of foam and sponge in different thicknesses and densities were vibrated for different masses of operators and various stimulation accelerations. Accelerations of the input and output signals were recorded and analyzed. Analysis of variance of input and output acceleration mean square was employed to examine the type of material used in seat cushion and the effect of different factors on them. Results of the study indicated that sponge reduced vibrations more for masses of 90 kg and higher, and foam decreased the vibrations more for masses below 75 kg. Also for acceleration over 6 ms-2 and lower values around 3 ms-2, sponge and foam are recommended, respectively. Moreover, thickness of 8 cm was the best choice for the cushion, and using the density of 30-50 kg m-3 was suggested.
