ASA 126th Meeting Denver 1993 October 4-8

3aUW9. A modified complex starting field for shipping traffic noise modeling.

Christopher J. Burkhalter

Naval Res. Lab., Code 7181, Stennis Space Center, MS 39529-5004

In current ambient noise modeling efforts, commercial shipping is considered a major contributor to overall noise levels and is modeled accordingly. The propagation of shipping noise from the many sources to the receiver is effected by use of any of a number of high-fidelity acoustic models. Almost all of these models require an initial condition in the form of a vertical pressure field that is stepped out numerically in range. This starting field usually takes one of several forms: a simple or modified Gaussian distribution around a source depth, a normal mode starter, a simple image (acoustic dipole) starter, or a Pade-approximated parabolic equation starting field. The implications of a near surface source are discussed, as well as effects of low- versus high-angle propagation models and the effects of complex reflection from the necessarily turbulent surface. Additionally, the use of the Gaussian distribution as a sufficient starting approximate is analyzed for long-range, deep-water results. [Work supported by ONR and NRL.]