Abstract:

Source localization can be a difficult problem in temporally and spatially varying shallow-water environments. The SWARM 95 data indicate that the acoustic fields at 225 and 400 Hz change drastically in the time scale of several minutes. Since it is practically impossible to model the replica field at this time scale, one expects degraded performance for matched field processing (assuming a time-independent replica field). An alternate processing scheme is proposed here. First it is shown that internal waves cause mode conversions and that mode conversions degrade matched-field source localization. This is illustrated for the Garret--Munk internal waves, the solitary internal waves and the combination of both. It is then shown that source localization can be achieved by using only the uncoupled modes. This concept was implemented using matched-beam processing. The beam filter serves to suppress the contribution of the coupled modes. It is shown that this technique significantly improves the localization performance over conventional matched-field processing. [Work supported by the Office of Naval Research.]