Ocean tomographic systems low frequency depth independent sound transducer source

Magnetostrictive ring transducers are known to be convenient for ocean exploration purposes, for instance, when used in CW tomography systems due to their reliability, robustness, deep water operation potential and low electrical impedance. But in the frequency range below 1 kHz resonance transducers dimensions become too large. This contradiction may be overcame by use of thin-walled cores (not more than 10 mm thickness for diameter of order of 1 m) transducers, where comparative yield of radiation water mass is underlined. The relation of frequency to geometrical dimensions of radiator and parameters of magnetostrictive material is obtained. This formula is proven to be correct in the limits 15-20 percent and it is confirmed by experiments with a series of ring transducers made of nickel-cobalt textured alloy with radius 100-1000 mm, different height and thickness. An available transducer, for instance, with diameter 1 m, height 250 mm, thickness 7.5 mm was tested to have resonance frequency 470 Hz and acoustical power 1.0 kW. A transducer with diameter 1.5 m, height 500 mm, thickness 6 mm was also tested to have resonance frequency 220 Hz and acoustical power 200 W. Estimated efficiency on resonance frequency was approximately 40% and up to 30% in the frequency band of approximately 10% width