Abstract: Flextensional acoustic source with sound-emitting surfaces (1, 2, 3, 4) adapted to be excited into vibrational movement, and for use in seismic exploration at sea. The source comprises a drive unit (21) being through the intermediary of at least one push element (22A, 22B) adapted to impose vibrational movement to the sound-emitting surfaces. Between at least one push element (22A, 22B) and the associated sound-emitting surface(s) (1, 2, 3, 4) there is provided a non-linear spring element (27, 28) the spring constant of which is controllable. Two oppositely acting push elements (22A, 22B) are arranged in axial alignment and preferably centrally in the source, and in addition thereto there are provided at least two tension elements (39, 40) with associated controllable, non-linear spring elements (35, 36, 37, 38) and being coupled to the sound-emitting surfaces (1, 2, 3, 4).

Abstract: Acoustic transmitter in particular for use in offshore seismic explorations, having sound-emitting surfaces (1, 2) being adapted to be subjected to vibrational movement by means of a drive unit (21) through at least one push element (22A, 22B) and two plate-like end pieces (3, 4) which are connected to the sound-emitting surfaces. The sound-emitting surfaces are formed by two curved plate members (1, 2) being of comparable width and heigth dimensions. The end pieces (3, 4) have a generally rectangular shape with a first pair of opposing side edges connected (5, 6, 7, 8) to end portions of the plate members (1, 2). Another pair of side edges on each end piece (3, 4) as well as side edges of the plate members engage two side plates (9, 10) which at either side closes the acoustic transmitter, preferably in a tightly enclosing manner.