The shallow water acoustic channel supports far-field propagation in a discrete set of
modes. Ocean experiments have confirmed the modal nature of acoustic propagation,
but no experiment has successfully excited only one of the suite of mid-frequency
propagating modes propagating in a coastal environment. The ability to excite a
single mode would be a powerful tool for investigating shallow water ocean processes.
A feedback control algorithm incorporating elements of adaptive estimation,
underwater acoustics, array processing and control theory to generate a high-fidelity
single mode is presented. This approach also yields a cohesive framework for evaluating
the feasibility of generating a single mode with given array geometries, noise
characteristics and source power limitations. Simulations and laboratory waveguide
experiments indicate the proposed algorithm holds promise for ocean experiments.