Ultra low frequency acoustic generator

An underwater acoustic signal generator comprising in combination:

• a source of pneumatic fluid at a high pressure relative to ambient water pressure;
• pressure equilibrium control means for providing pneumatic fluid at a reference pressure that is maintained substantially equal to ambient water pressure;
• pressure reducing valve means, connected to said source and responsive to said reference pressure, for providing pneumatic fluid at a regulated pressure that is maintained at a predetermined differential over said reference pressure;
• body means defining first and second chambers and a cylinder interconnecting said chambers;
• pneumatic oscillator means, connected to said pressure reducing valve means to receive penumatic fluid at said regulated pressure and connected to said equilibrium control means so as to exhaust at said reference pressure, for effecting substantially square wave pneumatic pressure excursions in said second chamber at a predetermined frequency;
• means for connecting the pressure equilibrium control means to said first chamber to provide pneumatic fluid at said reference pressure in said first chamber;
• a first piston having one side exposed to said reference pressure in said first chamber and the other side exposed to ambient water pressures;
• and
• a second piston disposed in said cylinder and connected directly to said first piston, said second piston being exposed on one side to pneumatic fluid at said reference pressure in said first chamber and on the other side to said pneumatic pressure excursions in said second chamber, whereby the effect of said pressure excursions on said second piston are transmitted through said first piston to said ambient water.