Stable data adaptive methods for matched field array processing in acoustic waveguides

The authors investigate the destabilization of J. Capon´s (Proc. IEEE, vol.87, p.1408, 1969) maximum likelihood estimator caused by the presence of correlated noise due to the excitation, by ambient noise sources, of normal mode (or local normal mode) structure in an acoustic waveguide. They develop an estimator-reduced maximum likelihood method that avoids the instability and presents the results of several simulations to illustrate the differences between the two methods. The results apply to any acoustic environment in which both signal and noise vectors are projected onto a subspace of lower dimension