Beginning in 1975, Munk and Carl Wunsch of the Massachusetts Institute of Technology pioneered the development of acoustic tomography of the ocean. With Peter Worcester and Robert Spindel, Munk developed the use of sound propagation, particularly sound arrival patterns and travel times, to infer important information about the ocean's large-scale temperature and current. This work, together with the work of other groups, eventually motivated the 1991 "Heard Island Feasibility Test" (HIFT), to determine if man-made acoustic signals could be transmitted over antipodal distances to measure the ocean's climate. The experiment came to be called "the sound heard around the world." During six days in January 1991, acoustic signals were transmitted by sound sources lowered from the M/V Cory Chouest near Heard Island in the southern Indian Ocean. These signals traveled half-way around the globe to be received on the east and west coasts of the United States, as well as at many other stations around the world.