A Prediction Model for Shallow Water Sound Transmission

摘要

For predicting the transmission loss to long ranges in shallow water with downward refraction, when only a frequency knowledge about the bottom is available, a theoretical model is derived leading to a particularly simple expression for the loss in terms of the water depth velocity gradient and bottom reflection loss at small grazing angles. This latter quantity, for which no measurements are extant, is approximated through computed curves of reflection loss at the boundary of a semi-infinite absorptive fluid. A test of the model is provided by two sets of field data. One consists of recent measurements by NEL at 1.5 kHz, along with core sample measurement of bottom density and sound velocity, in several Pacific Ocean areas. The other comprises a hitherto-unpublished transmission survey at 12 kHz made in 1944 by WHOI around our East and Gulf coasts. For this mass of data, the only information about the bottom is contained in words like 'mud' and 'sand'. Reasonable agreement with both sets of data is found. The model appears to be useful for making approximate predictions of transmission loss in shallow water. (Author)