Hot topics in underwater acoustics

Underwater acoustics is a ‘‘big tent’’ discipline that draws from, and makes contributions to, many diverse fields such as wave propagation, physical oceanography, signal processing and ocean engineering. In recent years, concern for the environmental effects on marine life has spawned research into both the effects of man‐made noise, and the use of active and passive acoustics to monitor biological activity. Special Sessions at this meeting reflect this diversity. This paper will draw on these Special Sessions to present some exciting examples of current research: (1) Parabolic equation methods for wave propagation, (2) robust passive sonar techniques, (3) inverse methods for determining geoacoustic parameters, (4) high‐frequency acoustic interaction with the sea floor, and (5) bioacoustic resonance. In signal processing, one of the most active areas is the exploitation of the concept of time‐reversal. In ocean engineering, there has been a tremendous increase in the applications for autonomous undersea vehicles. A brief overview of developments in these areas will be included. [Work supported by ONR.]