Elimination of background disturbances from measurement spectra

Performing measurements (as for instance vibration measurements) in harsh industrial environments can be a tough task. In contrast to controlled laboratory conditions, important disturbing background vibrations can be present. Since these disturbances are often very high in amplitude, the measurements can be useless, even if the frequency of the disturbance is separated from the actual frequency band of interest of the structure under investigation. Indeed, because of spectral leakage a single-frequency component can spread out its energy over a large frequency range. In this paper, a technique is proposed to eliminate background disturbances from measurements (although vibration measurements are considered in the paper the technique also works for general signals). The technique developed uses two periods of a periodic signal as the excitation signal. The odd frequency lines of the discrete Fourier transform of two periods are used to estimate a parametric model of the disturbance. This model is then used to correct the measurement. The proposed technique is validated on both simulations and vibration measurements of a car door.