Sonobuoy Measurements in Thin Layers

Abstract

The application of standard sonobuoy techniques to thin subbottom layers at 3.5 kHz requires modification of the usual method of analysis. For a thin layer in deep water (thickness ratios greater than 15),velocity computed by the standard t²(x²) method is sensitive to the detailed velocity structure in the water. An alternative approach, which compares paths of the same ray parameter rather than the same shot position, gives the solution for a subbottom layer independently of the velocity structure above the layer. The method has been tested on simulated layer structures and on actual sonobuoy data. The results indicate that the technique will be useful for thickness ratios as high as 100. Systematic variations in the results from real data suggest the possibility of lateral inhomogeneities in the layer structure.