Abstract : The long-term goals are to advance our understanding of the nature of high-frequency (8-50 kHz) sound propagation in the ocean waveguide, with emphasis on surface, bottom, and volume effects on the forward propagated field. The central purpose of the High-Frequency Channel-Characterization Experiment (HFX) is to learn as much as possible about the channel impulse response (or transfer function) and its dynamics. Ideally, we would like to characterize the behavior as a function of 1) source/receiver geometry, 2) arrival angle, 3) carrier (central) frequency, 4) ocean volume structure, 5) bottom type, and 6) boundary dynamics, including effects of surface waves and bubbles.