Abstract:
Sound propagation models have typically been used to develop noise control
solutions for a wide variety of troublesome sources from highways, power plants,
and airports to stadiums and outdoor amphitheaters. Almost all of these models
assume that there is no variability in the atmospheric properties of the
propagating medium but this assumption is almost invariably false. Predictions
from these models are usually validated during the day when propagation
conditions are favorable, producing lower levels than the models calculate. The
problems usually come at night, when temperature and wind variations in the
atmosphere create propagation conditions which are not favorable, resulting in
much higher noise levels in the community, often on the order of 15--20 dB. This
paper describes work which has been undertaken by the Walt Disney Company in an
effort to produce a more precise computer model for these unfavorable
conditions. The model developed is based on Gaussian beams, a hybrid technique
developed to retain some of the fundamental aspects of ray tracing while
incorporating some of the more advanced GFPE concepts. The fundamental code,
developed by Ken Gilbert and Xiao Di, is being integrated into