Research in underwater acoustic propagation and acoustical oceanography often involves use of sound
sources. Almost all of these programs are sponsored by the Office of Naval Research, and the information
obtained is of value for improving military sonar systems. The sound sources used for these studies are
either commercially available transducers or systems specially designed to meet specific research
requirements. A wide variety of signals, bandwidths, source levels, and duty cycles are transmitted during
these projects. The spatial extent of most experiments is tens of kilometers, but basin-scale projects such as
the Acoustic Thermometry of Ocean Climate (ATOC) program have also been undertaken.