Environmentally adaptive reverberation nulling using a time reversal mirror

Backscattering from the rough water-bottom interface can serve as a surrogate probe source in time reversal. A time-gated portion of the reverberation then is refocused to the bottom interface at the corresponding range [Lingevitch et al., J. Acoust. Soc. Am. 111, 2609–2614 (2002)]. In this paper, reverberation nulling is investigated to enhance active target detection without a priori knowledge of the environment. The basic idea is to minimize the acoustic energy incident on the corresponding scattering interface by applying an excitation weight vector on the time reversal mirror which is in the complementary subspace orthogonal to the focusing vector. Numerical simulations illustrate the potential of reverberation nulling using a time reversal mirror.