Sound spatial correlations in shallow water

A method is presented for the estimation of the vertical and longitudinal correlations averaged over range and depths in a multipath channel. The resulting correlations are shown to be the integral of the vertical and longitudinal correlation factors weighted by the angular energy density. A correlation peak occurs when the receiver depth approaches either the source depth or its conjugate. The longitudinal correlation is shown to be reciprocal while the vertical is not. Numerical results are developed to gain additional insight into the physical features involved. Some field measurements of spatial correlations obtained in North China Sea are included.