Abstract: 1. The method of producing an electric signal corresponding to the underwr acoustic signature which would be generated by the movement of a certain sound source through a remote underwater environment which comprises preparing a recording at a substantially constant signal level of the acoustic output of said certain sound source in deep water far from shore, preparing a series of curves of the transmission characteristics of said remote environment for sound in selected consecutive frequency bands as a function of distance from said source, reproducing the constant level recording as electrical waves, separating the reproduced electrical waves into said selected consecutive frequency bands, modulating the amplitude of the electrical waves in each frequency band in accordance with the corresponding sound transmission characteristic curve, and combining the modulated electrical waves.