Use of a twin-inverted pulse sonar (TWIPS) to discern between solid objects and bubbles

Abstract

This thesis shows how a twin-inverted pulse sonar (TWIPS) can take advantage of nonlinear bubble dynamics to suppress undesirable bubble clutter in sonar systems. This sonar requires the production of two high-amplitude pulses in short succession, the second of which must be 180° out of phase with the first. It will be shown that the echoes from these excitations can be combined to selectively suppress between even- and odd- harmonic energy. After a simulation is used to prove the TWIPS concept, an experiment will be described wherein this method was tested in a controlled environment on a replicated oceanic bubble cloud. The novel bubble-cloud generating machine will be described in detail. The results from a TWIPS sea-trial will then be used to show that the method works not only in controlled environments, but also in the open water. Finally, a review will explore newly-discovered links between the echolocation abilities of acoustically-active, coastally restricted cetaceans and TWIPS. That review will show using pre-existing data that some coastal dolphin species seem capable of generating pulse-pairs wherein the second pulse is 180° out of phase with the first.

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