Sound Propagation in an Ocean Environment with Fluctuating Sloping Bottom

The sound propagation in an ocean environment with fluctuating sloping bottom is studied in this paper. In an experiment conducted in the South China Sea, the experimental area exists a sloping bottom with fluctuations. The transmission losses (TLs) of the measured signals decrease when the source is at certain ranges. The TLs in the ocean environment with the real bathymetry and an approximate bathymetry neglecting the fluctuations on the sloping bottom are calculated. It is shown that the calculated TLs in the experimental environment agree well with the measured results, but the calculated TL of
$V_{z}$
using the approximate bathymetry is about 8 dB less than the measured results when the source range is 42.3 km. Theoretical analysis with the ray model show that the fluctuations on the sloping bottom generate eigenrays with small grazing angles and high energy at the receiver. However, there are no small-grazing-angle eigenray in the approximate environment, so that the TLs at the receiver are large. Therefore, the accuracy of bathymetry is significant for sound field prediction and corresponding applications.