English: An acoustic experiment in 1991 called the Heard Island Feasibility Test (HIFT) tested the ability of sound signals to measure ocean temperature. The coded signals transmitted during the tests traveled geodesic paths to several receivers located in the Indian, Pacific, and Atlantic Basins. The signals arrived on both coasts of North America. The transmission point, near Heard Island in the Southern Indian Ocean, was chosen to allow acoustic measurement of all the major ocean basins.