ASA 125th Meeting Ottawa 1993 May

5pUW10. Measurements of propagation loss in isothermal surface ducts.

F. D. Cotaras

P. D. Morash

J. B. Franklin

Defence Res. Establishment Atlantic, P.O. Box 1012, Dartmouth, NS B2Y 3Z7, Canada

Over the past several years, the Defence Research Establishment Atlantic has made measurements of propagation loss in surface ducts. The experiments were conducted at deep-water locations, and both the source (SUS charges) and receiver were placed in the duct. At the sites where the surface duct was well defined and constant with range, the data are in good agreement with a simple propagation-loss model. Inputs to the model include the sound absorption coefficient cited by Scheifele, Mellen, and Browning as well as the reflection-loss predictions of Brekhovskikh and Lysanov's method of small perturbations. The sea-surface was assumed to be described by a Pierson--Moskowitz frequency spectrum.