The AST was conducted to study the effect of internal waves on long-range acoustic propagation at different frequencies. Dr. Walter Munk of the Scripps Institution of Oceanography suggested that a controlled experiment be conducted to evaluate the effect. Dr. Mercer proposed the use of the JETI system. With ingenious signal design by collaborators from the University of Michigan, the JETI system allowed two frequencies to be simultaneously transmitted from the exact same location near Pioneer Seamount. This capability eliminated issues regarding the temporal and spatial variability of the internal wave field between the transmitter and the ATOC receiving network. The results are the first to demonstrate, unequivocally, the reduced effect by internal waves at lower acoustic frequencies. This was a collaborative effort with the Scripps Institution of Oceanography and the University of Michigan. The work was sponsored by the Office of Naval Research and the Advanced Research Projects Agency.