M.S. Thesis Presentation by Joseph A. Root
Friday, August 4, 2000

(Dr. Peter Rogers, advisor)

"Capabilities of an Underwater Acoustic Volumetric Array Using Time-Reversal Focusing"


Time-reversal invariance represents an extremely useful tool in the field of acoustics, and much time-reversal research exists. Likewise, a volumetric array represents another valuable tool in the field of acoustics, particularly underwater acoustics. However, researchers have yet to seriously explore combining time-reversal and a volumetric array in a single system. Thus, this research investigates the potential benefits offered by combining the time-reversal method with an underwater acoustic volumetric array. A potential application for this underwater acoustic volumetric array time-reversal mirror (UVATRM) involves acoustic imaging; useful for both underwater terrain mapping and naval mine hunting.

To gage potential benefits, a volumetric array was constructed with 27 2cm-diameter PZT elements mounted in a 3x3x3 cubic matrix configuration on a PVC frame. The system utilized synthetic methods to execute time-reversal and a scanning hydrophone to collect field data.

The UVATRM collected data during both acoustic focusing experiments and beamforming experiments. During these experiments, different array modifications introduced different levels of scattering into the field, testing the ability of time-reversal to penetrate the scattering. The results included broad band analysis of focal region characteristics like focal region length and width, and beam pattern characteristics like main, side, and back lobe height.