Abstract: An improved method of measuring the flow velocity of water bodies, characterized in that, in addition to a principal direct path along which acoustic signals are propagated across and through the direction of flow of water, an auxiliary indirect path for acoustic signals is utilized comprising two segments of an acoustic signal reflected at a water-air or water-ice boundary of said body of water.

Abstract: A method for troubleshooting an underwater acoustic transducer array comprising a plurality of transducers so as to test the operationally installed underwater transducer array on board for its operational reliability and to be able to localize malfunctioning transducers. For this purpose, a sinusoidal test signal, preferably the transmitted signal itself, is fed through a connecting line into the transducer array from a location remote from the transducer array and the current flowing through the transducers is detected by at least two samplings as the real component and the imaginary component with respect to the test signal. The sampling values are transmitted back to the remote location and the admittance of each transducer is determined from the ratio of the real component and of the imaginary component of the current to the test signal amplitude. A significant deviation from the known admittance at the test signal frequency is interpreted as a transducer malfunction.

Abstract: In a system composed of a plurality of sonar devices mounted on a ship and arranged to operate simultaneously, each device being composed of two units between which electrical signals pass during operation of the device and conductors connected for conveying such signals between the units, the conductors for all of the devices are constituted by a plurality of multiconductor cores, at least one core being associated with each device, and all of the cores are twisted together to form a common spiral multicore cable, whereby the spiral form of the cable produces a low level of cross-talk between the signals in different ones of the cores.