Acoustic scattering by ocean irregularities: Aspects of the inverse problem

Abstract

Expressions are derived for the autocorrelation and structure functions of the acoustic refractive index for ocean internal waves in the presence of fine structure. The transverse autocorrelation and structure functions required in acoustic scattering formulas are obtained from these. The spectra and correlation functions of acoustic phase, complex amplitude, and intensity are considered in the case of multiple scattering, and it is shown that the effect of fine structure on the fourth moment of the acoustic field is fundamentally different from that exerted on the second moment or the phase. The problem of deducing the correlation function of ocean irregularities from the acoustic signal is considered, and it is shown that, under certain circumstances, the full inverse problem can be solved by using the second moment of acoustic complex amplitude. Finally, the effect of tides on the phase, second moment, and the spectrum of intensity fluctuations of the acoustic signal is considered. It is shown that thi...