Timespread modeling of propagating pulsed and transient underwater signals

Many Navy standard and other widely used underwater acoustic propagation models were developed through an evolutionary process to address applications featuring narrow-band or single-frequency cw signals. A consequence of this development process is that, although the models may handle the originally intended problem very well, they are not necessarily able to describe the propagation of high resolution pulses or transients, where time-domain or multi-frequency FFT approaches seem called for. This paper presents the results of an evaluation of several propagation models to characterize short duration signals. The models tested represent a variety of physics-based approaches: parabolic equation, rays and Gaussian beams, modes, and hybrid approaches. The evaluation criteria include an ability of the modeling system to accommodate real-world, in-situ environments, accuracy of the results in the context of intended applications, and reasonable execution time.