OKI Electric Industry Co., Ltd., Electron. Syst. Lab., 688 Ozuwa, Numazu-shi, Shizuoka, 410 Japan
Japan Marine Sci. and Technol. Ctr., Yokosuka-shi, Kanagawa, 237 Japan
A superior underwater projector having low frequency, high power, high efficiency, and broad bandwidth for the Ocean Acoustic Tomography (OAT) system has been developed. The OAT system is proposed to measure temperature and current distributions of a wide range of sea area with a diameter of about 1000 km on real time by using sound waves. The projector vibrates in the radial mode of octagonal radiating plates connected with eight driving units having giant magnetostrictive rods. The projector is able to emit sound of more than 190 dB [0 dB=1 (mu)Pa-m] at a low frequency of about 200 Hz under the operation depth of about 1000 m when it is excited by electric input power of about 900 W. The performance is enough to cover the range of 1000 km for the OAT system. Also, the derived values from measurements are in good agreement with the calculations based on the simple equivariant circuit model.