The analysis of response to a forcing function that is neither harmonic nor periodic is comparatively more complex. However, for linear systems a general method exists which is conceptually quite straightforward. This method is based on the ability to obtain mathematical expressions for the response of the system to an impulsive force. A general forcing function is expressed as the sum of a series of impulses and the response to the applied force is obtained by superposing the responses to the individual impulses. Superposition, in fact, involves the evaluation of an integral, known as a convolution integral or Duhamel’s integral, either mathematically or by numerical means of integration.