Acoustic Room De-reverberation Using Time-Reversal Acoustics

This thesis probes the performance of one-channel time-reversal acoustics in a chamber in terms of the geometry of the cavity. In particular, a rectangular chamber is compared to an enclosure that has a stadium shape. The mode structure in the rectangular cavity is highly symmetric, while it is highly irregular in the stadium-shaped cavity. Time- reversal acoustic techniques produce an improved focus in the latter. The focusing quality is determined as a function of frequency, time-reversal window size, and spatial extent. A scheme for encrypted acoustic communication, both in air and underwater, that uses multiple broadband signals with identical bandwidth, Hanning window source spectra, and center frequencies separated by half the bandwidth, allowing for null detection between adjacent signals, is successfully investigated.Naval Postgraduate School Monterey CA is the author of 'Acoustic Room De-reverberation Using Time-Reversal Acoustics' with ISBN 9781423552383 and ISBN 1423552385.