Abstract: A low drag nose assembly for use with an acoustic homing torpedo in an aqus environment has at least one planar array mounted in the slanting side of a substantially conical support member and provides a plurality of preformed sonar beams which display an azimuth selectively extending from fore to aft simultaneously.

Abstract: The acoustical energy output of a source is varied in frequency between limits to sweep a frequency band encompassing cavity resonance conditions which depend on the quantity of a fluent material within a tank excited by such acoustical energy. The volume of the fluent material is calculated from the excitation frequency registered during verified detection of resonance conditions, based on abrupt changes in signal characteristics and stored data relating to the geometry of the acoustic sensor arrangement through which the tank interior is monitored.