Acoustic transponding simulated pebbles monitored by side scan sonar

An electroacoustic system was developed to assist in the study of lake bed material transport. The system consists of miniature acoustic transponders constructed to be replicas of natural pebble-sized bed material, larger benchmark transponders suitable for fixing to bottom mounted structures and a commercial side scan sonar. The transponders are interrogated by the 0.1 ms duration, 100 kHz signal transmitted by the side scan sonar and reply with a 1 ms acoustic burst (95 kHz). The transponder responses are received and recorded by the side scan sonar. The position of the pebble relative to the known benchmark array can be deduced from the display record. The useful range for this system is 20 m to 200 m.