Fabrication and test results of a conical acoustic lens

A narrow aperture liquid filled conical acoustic lens was desired to mount on the hull of an ocean going vessel, and to receive signals in the 20-40 Khz frequency band. The lens would contain approximately 60 individual hydrophone elements mounted in a circle, each operating with a beam 6° wide in the horizontal plane and 60° wide in the vertical. This paper presents information on fluid selection, design and construction of the case, window, fairing and sound absorbing lining and the results of acoustic tests. Testing was done at the Naval Surface Weapons Center Acoustic Facility at Triadelphia Reservoir.