ACOUSTIC SHADOWING BY SEAMOUNTS

Explosive acoustic sources were dropped from a ship traversing a course approximately perpendicular to a line from the ship to a hydrophone of the Pacific Missile Impact Locating System (P-MILS) near Midway Island. The rectified shot signatures recorded from the hydrophone were aligned for identification of arrivals and assignment to ray paths. The alignment revealed that some arrivals predicted by ray-trace calculations were missing from some signatures. The signals traveled across an area of seamounts located north of the Hawaiian Ridge and the missing arrivals are related to ray-path blocking. The blocked ray paths, and the specific seamounts responsible for the blockages, are identified for three selected shot signatures. The shadowing of the hydrophone by identifiable seamounts for CW signals from a towed, 14.65-Hz source is correlated with the blockage of propagation paths for the shot signals. © 1979 Acoustical Society of America