Abstract: A seismic method and apparatus utilizes two point sound sources located at the same location on the earth to produce sound waves at different amplitudes and times. The reflections of the sound waves are analyzed to determine the acoustic properties and rock boundaries within the earth.

Abstract: Method and apparatus for the generation of low frequency acoustic energy such as may be employed in carrying out seismic surveys in marine environment. In imparting an acoustic energy pulse into a body of water, a planar electroacoustic transducer having parallel transducer plates is employed. The transducer plates have conforming electrical conductive paths. An impulse of opposed current flow is applied to the conductive paths to produce an electromagnetic field between the conforming paths which forces the transducer plates apart, generating an acoustic impulse having a center band frequency of less than 350 hertz. The wave length of the acoustic impulse at this frequency is less than twice the major planar axis of the transducer. The conductive paths may be formed of elongated conductors which are oblong in cross section and cover most of the radiating surface of the transducer.

Abstract: Apparatus for generating vibrations in a medium, such as the ground, comprises a first member which contacts the medium, means, preferably electromagnetic, which includes two relatively movable members for generating vibrations in the apparatus and means operatively connecting the said two members to said first member such that the relatively amplitudes of the movements of said three members can be adjusted to match the impedances of the apparatus and the medium.