In this study the spectral properties of the hydrogen flow and electricity current data which are collected from a fuel cell system are extracted. The electricity current of the fuel cell system is in the DC character however, some noise effects like measurement noise and some disturbances that come from the input can be considered as an additional noise effects on the dc-component. For this reason, this research aims to define the noise types in the fuel cell system. In this manner the most interesting one is related to the process noise. Consequently, for considered measurement and experimental study, these noise intervals are categorized like the process noise (0-10 Hz); input disturbances (0-50 Hz) and Measurement noise (50-90 Hz).