ASA 125th Meeting Ottawa 1993 May

1aAO4. Considerations for shallow water propagation experiments.

T. Ewart

F. Henyey

D. Jackson

E. Thorsos

Appl. Phys. Lab., Univ. of Washington, Seattle, WA 98105

When one examines the issues involved in propagation of sound in shallow water, the conclusion is that the ever-present ocean bottom, with its inhomogeneity and anisotropy, will dominate. A single model with a few parameters will not be appropriate for all bottom types. This is unlike studies of scattering in the random ocean volume and from the sea surface, where simply parametrized models are useful. The presence of very large numbers of multipaths blurs the distinction between stochastic and deterministic issues. It is clear that one needs to understand the angular and temporal behavior of the acoustic fields in order to understand the channel characteristics for given source(s)/receiver(s) combinations. This implies that large aperture and broadband experiments will be required. Several issues must be addressed before designing such experiments. (1) Will the present simulation capability allow one to design a good experiment for the case of a reasonably homogeneous bottom? (2) How many multipaths are there, and can they be separated? (3) If there are a large aperature and bandwidth, can matched field or backpropagation methods of source localization work? (4) What are the rest of the questions? This group will conduct an experiment in Knight Inlet, BC, which will include preliminary shallow water measurements, and the plans for this experiment will be discussed.