Abstract: Towed low-noise linear acoustic antennas configured for seismic exploration. The jacket of this antenna is pierced with holes that allow seawater to enter the inside of the antenna. The hydrophones are isolated by enclosing them in polyurethane envelopes filled with oil or gel. Buoyancy is ensured by lightening the jacket with hollow inclusions formed from microspheres. Such a structure allows the output noise level of the hydrophones to be reduced by 15 dB.

Abstract: A system for underwater seismic prospecting or exploration on seafloors, especially deep seafloors, including streamers designed to contain the measurement devices and to lie on the seafloor, in the form of an inner tube that is non-stretching and non-compressible and an outer tube that is extensible to a certain extent. Through the injection of liquid between these two tubes, the buoyancy of each streamers is made positive. This enables it to be detached from the seafloor and towed to the next measuring position.

Abstract: A method for controlling the navigation of a towed linear acoustic antenna. Birds equipped with variable-incidence wings are fixed onto the antenna. Through a differential action, the wings allow the birds to be turned about the longitudinal axis of the antenna so that a hydrodynamic force oriented in any given direction about the longitudinal axis of the antenna is obtained. Power and control signals are transmitted between the antenna and the bird by rotary transformers. The bird is fixed to the antenna by a bore closed by a cover. The bird can be detached automatically as the antenna is raised so that the antenna can be wound freely onto a drum. This method allows the full control of the deformation, immersion and heading of the antenna.

Abstract: Methods for making linear acoustic antennas designed to be towed behind a boat, wherein open-cell foam cylinders (101) are opened lengthwise (103) and electroacoustic receiver modules (101) are placed therein. After closing the cylinders, they are arranged end-to-end and a series of layers of porous nonwoven material, reinforcing nets (111) and wiring cables are wound around the cylinder surfaces. Finally, a protective sheath is extruded onto the cylinders and their end portions are joined together. The manufacture of such antennas may thus be mechanised using cable technologies.

Abstract: A linear hydrophonic antenna with an associated portside/starboard ambiguity removing device comprises three streamers placed in an equilateral triangle, with a center distance of the order of a third of the wave length which corresponds to the center frequency received. The density of the median streamer is notably greater than the common density of the other two streamers. Channels are formed in a standard way, and the received signals are phase shifted then added up so that the directivity associated with each channel shows a zero, either at portside or at starboard, the direction of which remains fixed despite the roll.

Abstract: A vibration damper is provided for a towed body usable more particularly as head section of an underwater antenna towed by a boat and containing detection and measuring instruments.The damper of the invention comprises at least one piece with high loss angle in contact with a traction element so that vibrations perceived by the traction element cause deformations of said piece.