Improvement of impulse response spectrum and its application

Since the impulse response of a system is a transient and non-stationary signal, difference of record length makes the unit impulse response spectrum of the system to be not unique. It means that the magnitudes and phases of the frequency response function obtained from impact hammer testing depend on the record length. Whenever the record length is not longer than the duration time during which the impulse response completely diminishes, 'finite record length error' takes place in the impulse response spectrum. In this paper, the finite record length error is theoretically verified and a new method reducing the error is introduced. The system parameters to induce the finite record length error are investigated, and an optimization method is also proposed to reduce this error. Numerical and experimental examples are carried out to show the characteristics of the finite record length error and the validity of the new method proposed in this paper.