Abstract: The vertical beamwidth of the received beam of a return signal of a sonar system is adaptively modified as a function of water depth, altitude and range. The received beam is also vertically steered as a function of altitude and is steered at least once prior to the adaptive modification of the beamwidth. The vertical aperture is thereafter grown as a function of range by increasing the number selected elements in the hydrophone array. This is achieved by dynamically controlling a vertical beamformer by controlling the number of elements selected and the vertical steering angle in response to sensors which provide, among other things, data as to water depth, altitude or sonar depth, platform dynamics, and sonar range/time.

Abstract: A hydrophone array wherein each individual hydrophone of the array is comprised of, e.g. polyvinylidine fluoride (PVF.sub.2), tiles bonded to a substrate member opposite one another on opposite surfaces of the substrate. The substrate is a relatively stiff, metallic member having a Young's modulus of at least an order of magnitude greater than the PVF.sub.2 tiles which are oriented such that their stretch directions on either side of the substrate are parallel to one another. The directions of polarization of the tiles are either the same or opposite and electrical connections are made such that for a predetermined relative orientation of the directions of polarization, any output signal which may be caused by flexing or acceleration of the substrate is substantially reduced or eliminated.

Abstract: A sonar system for positive identification of certain resonant body targets such as mines. Two acoustic signals of different frequencies are transmitted toward the target and the acoustic returns are separated into the component frequencies, detected, and thereafter subtracted from one another. A signal, above a threshold value, resulting from the subtraction is indicative of a resonant body target and the indication is displayed and/or recorded.