Determination of equivalent sound speed profiles for ray tracing in near-ground sound propagation

Abstract

The determination of appropriate sound speed profiles in the modeling of near-ground propagation using a ray tracing method is investigated using a ray tracing model which is capable of performing axisymmetric calculations of the sound field around an isolated source. Eigenrays are traced using an iterative procedure which integrates the trajectory equations for each ray launched from the source at a specific direction. The calculation of sound energy losses is made by introducing appropriate coefficients to the equations representing the effect of ground and atmospheric absorption and the interaction with the atmospheric turbulence. The model is validated against analytical and numerical predictions of other methodologies for simple cases, as well as against measurements for nonrefractive atmospheric environments. A systematic investigation for near-ground propagation in downward and upward refractive atmosphere is made using experimental data. Guidelines for the suitable simulation of the wind velocity profile are derived by correlating predictions with measurements.

Outdoor sound propagation with analytic ray curve tracer and Gaussian beam

“…With the analytic ray curve tracer 6 as a component, our method inherits its many potential extensions, such as: augmenting GA methods with capability to handle inhomogeneous media; forming hybrid method with ESM based on frequency and spatial subdivision (similar to Yeh et al 35 ); using the ray tracer for wide area assessment that guides the application of numerical methods only in areas of interest. As in other ray models, extensions 47,48 to our method can also be built to account for dynamic turbulence fields. It is also possible to accommodate sound sources other than a point source, such as complex sources or sources with directivity; 49,50 this can be achieved by using the techniques of Gaussian beam expansion.…”

Sound Synthesis, Propagation, and Rendering: A Survey

“…They then use the numerical grid division to integrate the changes of the shape of the complex terrain and acoustic velocity into the discrete path. Prospathopoulos et al [156] used ray tracing method to determine the sound profile in the near earth propagation modeling, and more accurately simulated the near earth sound field. Mo et al [129] considered the influence of wind, temperature, and other environment factors, combined the adaptive grid with parabolic ray tracing, and solved the problem of nonlinear sound propagation.…”