EMISSION OF SOUND BY A SEMI-SUBMERGED OBJECT IN SHALLOW-WATER

A semi-analytical solution to the problem of noise emission by a finit e size object in shallow water is described. The acoustic field near t he object is formulated in spherical coordinates. An inner region is s et up to satisfy bottom boundary conditions and the normal mode soluti on of the outer region is matched at some distance from the source. Se veral numerical examples related to noise emission from bubble clouds are given. Comparison with the method of images shows excellent agreem ent up to a certain distance from the source where the image solution is expected to be accurate. The technique is also extended to handle a rbitrary sound-speed profiles in water column by means of a novel meth od for calculating normal modes. The point source approximation that h as been widely used in the literature is also discussed by comparing t he normal mode coefficients. It is found that the validity of the poin t source solution depends very much on the local radiation characteris tics of the source. (C) 1996 Acoustical Society of America.