Passive-sonar signal simulation using frequency-domain techniques

Describes a real-time passive-sonar simulator. Most of the processing involved in the simulator is carried out in the frequency domain; the arguments for doing this are presented. The spectrum of noise radiated by a target vessel can be modelled as a frequency spectrum in which the spectral components are generated stochastically. Propagation effects are also modelled in the frequency domain. While it is possible to produce a model containing multiple paths where differential time delays and transmission losses are incorporated, it is more efficient to generate the propagation model stochastically. Similarly, the spectrum of the ambient noise is also generated stochastically. This noise spectrum is added in the frequency domain to the received signal spectrum and then an inverse Fourier transformation is made to generate a time waveform which models the output from a single hydrophone