Long Range Acoustic Propagation Program

Today, an understanding of acoustic programs of the ocean can be learned from any one of a number of textbooks, but in the
relatively recent past much of today’s knowledge is unknown. The Long Range Acoustic Propagation Program (LRAPP) was a major
contributor to today’s knowledge and was arguably responsible for some of the key technical developments that blunted the Soviet
submarine threat during the Cold War. The strength of the program was twofold. First, its unique combination of military personnel
and applied scientists from universities, Navy and university laboratories, and government contractors, and second, its management
by OP-095 (Manager, AntiSubmarine Warfare), an organization focused exclusively on the ASW mission to be accomplished. OP-095
was a rare example of true “out of the box” managerial thinking in that era. The LRAPP team (less than 200 people over 25 years)
developed models for acoustic propagation and ambient noise prediction from first principles. Subsidiary models on worldwide
shipping distributions, and measurements of radiated noise of submarines and surface ships allowed ambient noise predictions of
levels as a function of depth. These models, and others, were all validated in a large number of extensive ocean exercises (96) with
data collection that included direct measurement of sound speed, detailed measurements of the bathymetric profile, and basin shipping
distributions, in addition to temperature and salinity data as a function of depth. The measurement and accurate prediction
of directional ambient noise as a function of depth was a novel concept at the time. This characterization led to advances in array
processing that resulted in significant improvements in array performance in real-world operations. This combination of validated
scientific research and its translation and acceptance by the operational Navy provided the successful ASW program that the United
States needed during the Cold War.

U.S. Navy Journal of Underwater Acoustics Volume 61, No. 2 April 2011

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