The experimental determination of the frequency response functions in mechanical systems requires accurate experimental tests. In this paper, an experimental study of the optimal parameters of a sine sweep excitation generated by an unbalanced mass excitation device is presented. In order to evaluate the accuracy of the frequency response functions, non-parametric identification method is used to find a good signal-to-noise ratio and a best confidence region of the estimated frequency response functions. For this, an experimental test-rig based on mass-spring-damper system excited by an unbalanced mass excitation device has been designed and implemented at the laboratory. Then, linear sweep is used to control the rotating speed of the unbalanced system generating a sweep sine harmonic excitation. The proposed study of the experimental methodology demonstrates that excitation parameters such as amplitude, sweep rate and test time affect signal-to-noise ratio, reducing the accuracy of the measured frequency response functions in the case of noisy environment