At first, required conditions for the source of the acoustic tomography of 1000km scale are estimated by the use of the sonar equation. The results obtained are as follows; the frequency is 200Hz, sound pressure level is 190dB and Q is below 4. Using the cylinder source of pulsating barrel type with several driver units and vibrating masses, conditions to realize the sound pressure level above 190dB and the source diameter within 1 m are calculated. At the result of the estimation with the physical parameters of several kinds of magneto-strictive materials, it is shown that the super magneto-strictive material is the only material to satisfy the required conditions. After constructions of the source for pressure balance in deep sea are discussed experimentally, the air cavity is added inside the cylinder source and the pressure compensator is adopted to compensate the pressure change in the air cavity according to the water depth.
Next, sea trials of the developed sound source are carried out in Suruga Bay, and obtained results are as follows; the change of the resonant frequency relative to water depth agrees well with the calculated value, and then it is shown that the change is corresponding to the stiffness in the air cavity. It is shown that the sound pressure level above 190dB is obtained in the range of the water depth between 800m and 1200m and the frequency between 180Hz and 240Hz. And it is confirmed that the Q of the source is below 4 at the resonant frequency in the each depth. At last, the long distance propagation test of 621km was carried out in the east of Izu-Ogasawara area, and receiving signal was obtained with sufficient SN ratio.

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