ASA 127th Meeting M.I.T. 1994 June 6-10

3aUW11. Range variation in a numerical average underwater acoustic propagation method.

Roger M. Oba

Naval Res. Lab., Stennis Space Center, MS 39529-5004

A computational method of numerically computing average complex pressure field has been developed using a normal mode analysis of the forward propagating solutions of the Helmholtz equation [R. M. Oba, Acoust. Lett. 16, 56--61 (1992)]. It computes the transmission loss and phase for the average solutions in the continuous wave case in piecewise range-independent cases as well as a case of rapid fluctuations in range. Suppose the uncertainty can be probabilistically modeled within range intervals as ensembles of sound speeds. If for each sound speed in the ensemble the variation within each interval is relatively small, and if the variations within the ensemble are uniform, then modification of the existing method allows computation of average volumetric forward and backward propagation. This technique will be useful in matching this computed average field at some final range to a deterministic solution starting from that range on. This technique can also be used in the limit of small intervals of uncertainty. [Work supported by Naval Research Laboratory and the Office of Naval Research.]