The invention relates to a simulator for providing waveforms of the type produced at a receiver from a sonobuoy transmission. The simulator signal includes a component representing reverberation under different sea state conditions and a component representing echo pulses received from a target having relative motion with respect to the sonobuoy. Selected initial range and target speed values can be set in the simulator so that the signal includes a sequence of echo pulses having the varying delay and doppler shift which would occur from a target starting at the selected range and moving at the selected speed.