A spatial impulse response model of the parametric array is developed and used to give physical insight into its behavior when operated in a transient mode. Experimental measurements of the spatial dependence of the acoustic pressure waveforms produced by the transient parametric array are compared with the result of the convolution of the spatial impulse response with the specific pressure waveforms used. Particular emphasis is given to the case where the primary field is discontinuously terminated. In such cases effects due to the finite aperture of the parametric array and effects due to its termination may be seen by a point hydrophone either as separated or superposed events in time, depending on the geometry, when the parametric array is operated in the transient mode. Although the impulse response model is restricted by various assumptions, it can contribute to an understanding of the parametric array operation under more general circumstances.