Abstract:

During the next several years the U.S. Navy will be installing large area O(1500 km[sup 2]) shallow-water training ranges off the U.S. mainland. These ranges require underwater acoustic tracking of targets to an accuracy of 100 m. Tracking will be performed via high-frequency pingers (10--50 kHz) located on the targets and bottom-mounted hydrophones (nodes). Development progress on a novel acoustic range-bearing node was presented by the authors at the December 1996 ASA Conference (Hawaii). The node consists of a compact concrete structure containing a minimum number of sensors (4) and implements an axisymetric acoustic horn. Further advances in the development of the device are presented here. Additional results of data processing from testing of the prototype device and results of in-air acoustic tests will be shown. A second prototype, which is currently being constructed, will be described. The design incorporates a modified horn shape, an acoustic window and support structure, and integral ``tone-pilz'' type stacked crystal transmitters located in the horn.