ASA 124th Meeting New Orleans 1992 October

3aUW15. Attenuation of low-frequency sound in shallow water.

Robert H. Mellen

David G. Browning

Marine Sci. Inst., Univ. of Connecticut---Avery Point, Groton, CT 06340

The dominant low-frequency sound absorption mechanisms in seawater are pH dependent. Since, for a given depth, pH values can vary significantly from ocean to ocean, the corresponding attenuation will vary also. This is most striking at the depth of the deep sound channel axis where, for example, the values of low-frequency attenuation in the North Pacific Ocean are only one-half those in the North Atlantic. Surface waters throughout the oceans, however, have a uniformly high pH due to universal interaction with a well-mixed atmosphere. As a result, shallow water of all oceans should have a relatively uniform and high attenuation. This attenuation is similar to measured values in deep water surface ducts. Examples are given for several shallow-water locations.