These experiments were made to study the application of pulse compression and continuous profiling techniques to deep-sea geophysical research. Tests were made in several areas with low- and high-frequency sources. Reflection profiles with a 125-cps source were made in the Straits of Florida. The receiving hydrophone was towed behind the ship. The hydrophone consisted of a 75-ft long array of 25 equally-spaced acceleration-balanced barium titanate elements inside an oil-filled hose. The source transmitted either a ping or a chirp coded ping. The receiver included a shift-register type of matched filter. Profiles were taken with both short pings and with chirp pings. The signal-to-noise gain of the chirping matched filter system was at least 12 db. Profiles were taken with a 400-cps source and the low frequency source in Long Island Sound to compare operations with different source frequencies. The 400-cps source did not penetrate beneath consolidated sediments whereas the low-frequency source did. The 400-cps source was used to study the reflections from the 15,500-ft deep bottom in the basin near Eleuthera, British West Indies. Reflections at sub-bottom depths of about 75, 300, and 800 ft were observed. The shallow reflector was irregular in depth and appearance.

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