Marine Sci. Inst., Univ. of Connecticut, 1084 Shennecossett Rd., Groton, CT 06340-6097
Transverse decorrelation of sound pressures signals received at horizontally separated points is investigated in shallow water in the presence of surface wind waves. By applying the adiabatic approximation and smooth-average method, the relationship between the transverse correlation and surface-wave frequency-direction spectrum is developed. Both surface scattering and multipath interference are involved. Since surface scattering degrades the correlation but multipath interference enhances the correlation as range increases, three range regions or zones are suggested: (1) near-field region in which normal modes or paths with large grazing angle are important, (2) multipath interference region in which the effective propagating modes or paths are degraded due to bottom reflection loss, and (3) surface scattering region in which the waveguide modes become dominant. The correlation has also been shown to be strongly dependent upon wind speed, bottom reflection loss, and frequency.