ASA 124th Meeting New Orleans 1992 October

1aUW3. Contribution of bottom-refracted sound to oceanic sound propagation.

J. I. Arvelo

Alliant Techsystems, Inc., Advanced Technology Ctr., 1911 Ft. Myer Dr., Arlington, VA 22209

J. R. Yuan

X. L. Bao

H. Uberall

Catholic Univ. of America, Washington, DC 20064

In the deep ocean, sound from an underwater source is channeled in the SOFAR channel to form a long series of convergence zones. These may be influenced by bottom reflections when the propagation occurs down a sloping ocean floor. Experiments [W. M. Carey, J. Acoust. Soc. Am. 79, 49 (1986)] show important residual intensities (~10 dB excess) between convergence zones whose origin could not be conclusively explained by downslope conversion, but could have been due to ``refraction'' (bottom penetration). Earlier pulse return experiments by Christensen et al. [J. Acoust. Soc. Am. 57, 421 (1975)] conclusively established the presence of bottom penetration effects in the presence of upward-refracting sound-speed gradients in ocean-floor sediments from a flat, deep (4000-m) ocean floor. In the present model calculation, carried out for the Christiansen deep-water case by using normal-mode and fast-field models, the influence of a shear-supporting, upward-refracting ocean floor on oceanic sound propagation, including the long-range presence of inter-convergence zone residual sound fields caused by bottom penetration is demonstrated. [Work supported by the ONT.]