Acoustical Society of America, Spring 1999 Meeting
Title: The experimental demonstration of selective mode excitation in a shallow water environment
Authors: James C. Preisig, John R. Buck, Mark Johnson, Hu Dou

The ability to selectively excite single acoustic modes in a shallow water environment is demonstrated and analyzed. Using vertical source and receiving arrays and the feedback control techniques based on those in [J.R. Buck, et. al., IEEE Journal of Oceanic Engineering 22, 281-291 (1997)], acoustic modes one through three were excited sequentially for periods up to 20 minutes with a fidelity of approximately 60 dB for mode one to 25 dB for mode three. The filtering of the received signal used in the feedback loop by projection into the subspace spanned by the dominant system modes was found to significantly improve the system's performance. This result will be explained and analyzed. The requirement for phase stabilization of the sampled received signal is also presented. The ability demonstrated here for high fidelity selectively controlled modal content of a transmitted acoustic signal offers potential for new methods for acoustic tomography and for studying underwater acoustic propagation. [Work supported by ONR Ocean Acoustics.]

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