Parabolic Equation Predictions Compared with Acoustic Propagation Measurements from Project Tasman Two.

摘要

The parabolic equation method for computing acoustic propagation losses was used to model the results of the Tasman Two Sea Tests. In these tests aircraft dropped SUS (signals, underwater sound) charges along four great circular paths from a hydrophone near South Island, New Zealand, in westerly directions across the South Tasman Sea and Southeast Indian Ocean. The data were processed in 1/3 octave bands from 16 to 1000 Hz. The best available sound speed, bathymetric, and sediment data were compiled both from Tasman Two Sea Tests data and from historical data. These data were used to make parabolic equation runs along the radials starting at the stationary receiver for 63 and 125 Hz. Great care was required in progressing down the continental slope from the receiver and over sea mounts where small step sizes in the numerical solution were required. Accurate modeling of sediments was also required in these areas. In the immediate vicinity of the hydrophone a ray theory for a wedge gave better starting values for the parabolic method than did a normal mode technique. Agreement between computations and experiment was generally good enough to substantiate the techniques used. Poor agreement for the most southerly radial suggested inadequate knowledge of the bathymetry and sediments within 200 km of the hydrophone. Shadowing behind seamounts was found to be strongly dependent on the nature of the sediment cover. (Author)