Effect of near-source bottom conditions on long-range sound propagation in the ocean

Underwater shots fired off Point Arena, California, were recorded on Sofar depth hydrophones at Eniwetok, Midway, and Oahu. Variations of 15 db in peak amplitude were noted on the records. The strongest signals were received from shots fired over the edge of the continental shelf in 90–275 meters of water. Variations in observed signal level are attributed to changes in bottom slope, bottom material, and water depth in the source area.