Abstract: Disclosed is an echosounder configured to: a) drive the transducers of its emitting antenna to emit first and second acoustic waves having first and second frequencies, these waves being superposed over one another along an axis of superposition that is directed toward a point of the bottom of the subaquatic environment, and b) acquire an echo signal, the frequency of which is equal to the difference between the first and the second frequencies, the echosounder being configured to perform steps a) and b) a plurality of times while varying the orientation of the axis of superposition, and to determine, on the basis of the acquired echo signals, an image representative of the content of the sub-bottom of the subaquatic environment beneath each of the points. Also disclosed is an associated method for characterizing a portion of the sub-bottom of a subaquatic environment.

Abstract: Disclosed is a broadband underwater acoustic transceiver device. The device can be used in particular for positioning, detection, range finding or underwater acoustic communication. The device coaxially combines, within a transceiver device, a Tonpilz transducer and a FFR transducer, the FFR being arranged in front of the transmission face/horn of the Tonpilz transducer. In such a configuration, the Tonpilz horn also acts as reflective tape for the FFR transducer, forming a common tape-horn element. Furthermore, an annular baffle surrounding the Tonpilz pillar creates a Helmholtz cavity for broadening the emission band towards the low frequencies.

Abstract: Disclosed is a marine surface drone including: - an on-board multi-beam sonar; - a system for controlling the sonar, configured to command, for a given position of the drone, a plurality of consecutive transmissions of acoustic waves, the control system controlling the sonar transmitters so as to vary the characteristics of the transmitted acoustic waves, from one of the transmissions to the next, and - an acquisition unit configured to determine, from echo signals acquired in response to the plurality of transmissions, a three-dimensional image representing the content of a given observation volume. The invention also relates to a method for characterising an underwear environment, implemented by such a drone.

Abstract: Disclosed is a broadband underwater acoustic transceiver device. The device can be used in particular for positioning, detection, range finding or underwater acoustic communication. The device coaxially combines, within a transceiver device, a Tonpilz transducer and a FFR transducer, the FFR being arranged in front of the transmission face/horn of the Tonpilz transducer. In such a configuration, the Tonpilz horn also acts as reflective tape for the FFR transducer, forming a common tape-horn element. Furthermore, an annular baffle surrounding the Tonpilz pillar creates a Helmholtz cavity for broadening the emission band towards the low frequencies.

Abstract: An electroacoustic transducer submersible in an immersion fluid (8) for underwater acoustic communications, includes two horns (3a, 3b), a counterweight (4), two electroacoustic motors (1a, 1b), aligned along an axis of symmetry (6), the opposite ends of the motors being respectively connected to a horn, the unit consisted by the electroacoustic motors, the counterweight and the horns being able to generate a longitudinal electroacoustic resonance mode. The transducer includes a rigid and hollow cylindrical part (5) extending around the counterweight, the cylindrical part having an axis merged with the symmetry axis of the transducer, the inside of the cylindrical part forming a fluid cavity able to be filled with the immersion fluid, the electroacoustic motors and the cylindrical part being so dimensioned that the fluid cavity forms an acoustic coupling between the longitudinal electroacoustic resonance mode and a circumferential resonance mode of the cylindrical part.

Abstract: An acoustic wave transducer includes at least one electroacoustic motor, a horn having an inner wall and an outer wall, a counterweight, and a hollow housing having an inner wall and an outer wall and at least one acoustic opening. The electroacoustic motor is connected to the horn and to the counterweight along an axis, and the electroacoustic motor is capable of exciting the horn at about at least one resonance frequency. The housing is connected to the counterweight and surrounds the motor and the horn, the outer wall of the horn being arranged opposite an acoustic opening of the housing, and the space between the inner wall of the housing and the inner wall of the horn defines a cavity that contains a fluid. The transducer includes acoustic attenuation elements connected to the outer wall of the housing in order to attenuate the emission and/or reception acoustic waves at the frequency at least in a direction transverse to the emission/reception axis.

Abstract: An electroacoustic transducer submersible in an immersion fluid (8) for underwater acoustic communications, includes two horns (3a, 3b), a counterweight (4), two electroacoustic motors (1a, 1b), aligned along an axis of symmetry (6), the opposite ends of the motors being respectively connected to a horn, the unit consisted by the electroacoustic motors, the counterweight and the horns being able to generate a longitudinal electroacoustic resonance mode. The transducer includes a rigid and hollow cylindrical part (5) extending around the counterweight, the cylindrical part having an axis merged with the symmetry axis of the transducer, the inside of the cylindrical part forming a fluid cavity able to be filled with the immersion fluid, the electroacoustic motors and the cylindrical part being so dimensioned that the fluid cavity forms an acoustic coupling between the longitudinal electroacoustic resonance mode and a circumferential resonance mode of the cylindrical part.

Abstract: The invention relates to an acoustic wave transducer that includes at least one electroacoustic motor (1, 21), a horn (4, 24) having an inner wall and an outer wall, a counterweight (5), and a hollow housing (8, 28) having an inner wall and an outer wall and at least one acoustic opening. The electroacoustic motor is connected to the horn (4, 24) as well as to the counterweight (5) along an axis (7), and said electroacoustic motor (1, 21) is capable of exciting the horn at about at least one resonance frequency f. The housing (8, 28) is connected to the counterweight (5) and surrounds the motor (1, 21) and the horn (4, 24), the outer wall of the horn being arranged opposite an acoustic opening of the housing, and the space between the inner wall of the housing and the inner wall of the horn defines a cavity that contains a fluid.