ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

2aUW5. Shallow water measurements of time spreading at high frequency.

Paul C. Hines Arthur

J. Collier

James A. Theriault

Defence Res. Establishment Atlantic, P.O. Box 1012, Dartmouth, NS B2Y 3Z7, Canada

Time spreading measurements provide an indirect measure of the acoustic bandwidth that can be supported by the water channel, which is critical to the design of sonar systems. Time spreading measurements were collected in a water channel 100 m deep, off the coast of Nova Scotia. Data were collected at frequencies of 20--22 kHz, 27--29 kHz, and 35--37 kHz using linear FM pulses 2 s in duration. The experiments were part of a collaborative trial conducted by Canada, the US, and the UK. Canada's Seahorse array, an anchored, high-frequency active sonar was employed for the source-receiver, and a UK free drifting echo repeater was employed for the target. Source-receiver and target position were recorded using a portable target range operated by the US. In the paper, time spreading measurements are compared with estimates obtained from the generic Sonar Model (GSM) for the experiment geometry. The GSM estimates of time spreading due to multipath propagtion compare favorably with the experimental data. However, time spreading of individual paths beyond that predicted by GSM is also evident.