This paper proposes an application of the inverse analysis to estimate the elastic response ahead of the crack-tip of a one-point bend specimen. The difficulty of the problem lies on determination of the impulse response function that relates the elastic response to a unit applied impact force which is numerically ill-posed. Two iterative numerical regularization schemes are proposed, first is a time-domain regularization based on the conjugate-gradient method and second is a frequency-domain regularization based on an optimal filter approach. Both schemes are evaluated by using the data obtained from an impact experiment. The result shows that the estimation error is about 18.0%.