Modal scintillation index: A physics-based statistic for acoustic source depth discrimination

A new discriminant based on the scintillation of normal mode amplitudes is introduced for the problem of passive surface/submerged source classification in a shallow water waveguide. The scintillation of modal energies is often used to characterize and understand acoustic wave propagation in a randomly fluctuating ocean waveguide [D. B. Creamer, J. Acoust. Soc. Am. 99, 2825 (1996)]. This paper proposes a variant of the traditional modal scintillation index to treat the discrimination problem in a typical littoral oceanic waveguide. The approach is based on a modal decomposition of fluctuations in the received pressure field associated with the temporal modulation of the depth of an acoustic source about its mean value. Source depth fluctuations are the result of a platform’s response to surface or internal wave motion. The rms mode excitations due to source depth modulation are shown to exhibit a depth dependent signature that may be exploited to statistically separate surface and submerged source classes...