SOUND-PROPAGATION OVER IMPEDANCE DISCONTINUITIES WITH THE PARABOLIC APPROXIMATION

Long-range, low-frequency sound propagation over varying terrain condi tions is an important problem with both civilian and military applicat ions. This work, considers the modeling of cw acoustic signals as they propagate over variable-impedance topography. The NASA implicit finit e-difference (NIFD) implementation of the parabolic approximation soun d propagation model that incorporates variable-impedance ground surfac es was used. The accuracy of this numerical model is demonstrated with a pair of test problems. An application of the results is used to pre dict excess attenuation of pure-tone signals whose propagation path in cludes portions of a flat lake surface. (C) 1996 Acoustical Society of America.