System for generating and transmitting acoustic signals underwater

A system for generating and transmitting acoustic signals under water which comprises a vertical array of spaced sources extending over a sizable depth range, which sources are either all air guns or all spark discharge devices, each of said guns possessing a gas charge chamber of the same or similar size for the storage of compressed gas under high pressure, each of said spark discharge devices being of substantially equal energy rating or size, said volume of compressed gas in each of said guns and energy from said spark discharge devices being explosively released upon command of a control signal from a source controller to provide a vertical distribution of gas or water vapor filled cavities, said explosive release resulting in an initial positive acoustic impulse from each source followed by a negative going undulation whose period is related to the depth of the respective cavities, said vertical distribution of cavities forming a stagger-tuned array of cavities whose decaying oscillations creates a sensibly broad spectral pedestal extending in period from the period of the acoustic oscillations from the upper-most cavity in the array to the period of the acoustic oscillations of the lower-most cavity in the array.