Dr. Thomas Rossby at the Graduate School of Oceanography at the University of Rhode Island will undertake a project to to purchase and evaluate a new flextensional acoustic transducer for possible use as sound sources for RAFOS navigation during the World Ocean Circulation Experiment (WOCE). Neutrally buoyant drifters are planned to be one of the major techniques for studying the subsurface and deep ocean circulation during WOCE. Numerous RAFOS drifters will be deployed and set to float at different depths. Their trajectories over periods of up to two years can be determined by analysis of arrival times of acoustic pulses emitted from fixed and precisely tuned transducers. Presently available transducers work well in regional studies. WOCE objectives call for basin-scale studies, so transducers having greater range are needed. The new transducer design makes use of new flextensional technologies and materials. Features of the new system include a very high sonic power level, high energy conversion efficiency, high bandwidth, and manageable size. Once purchased, a program of testing for long-term reliability and performance evaluation will be undertaken. Reliability tests involve attaching the transducer to a mooring and deploying it at 700 meters depth along the New England escarpment. Signals will be received and analyzed at an established listening station at Bermuda and the timing of transmissions will be set to support an ongoing long-term research project. After six to twelve months of deployment, the transducer will be recovered and examined for physical integrity and wear. Range tests will be conducted by lowering the transducer package at different depths from 2800 to 4300 km away from a receiving site. Measurements of radiated pressure levels will be made at each depth to understand the transducer's performance at increasing hydrostatic pressures. Transmitted signals at the varying distances will also be received and analyzed at the Bermuda listening station.
