Wavefront tracing for undersea acoustic propagation

Abstract

An acoustic wavefront tracing algorithm and corresponding computational implementation is presented. Similar to ray tracing and beam tracing, wavefront tracing casts independent rays that refract through the medium and reflect from boundaries. However, with wavefront tracing these rays step congruously and are connected as a triangulated surface. As this triangulated surface moves through space and time it contacts boundaries, receivers, or other points of interest, thereby providing all possible paths from the source. As each triangle steps forward, three space-filling tetrahedra are formed and acoustic properties are then linearly interpolated via barycentric coordinates. This interpolation also applies at a boundary surface, allowing for both specular reflection and diffuse scattering. The algorithm is derived from the wavefront construction method, in which the triangulated surface is adaptively modified to maintain a desired level of detail. However, by keeping the wavefront topology fixed, along with an efficient encoding of the algorithm, highly detailed simulations with millions of triangles are achievable. Borrowing from the computer graphics community, a bounding volume hierarchy is used to accelerate the computation of ray–boundary intersections. An example simulation of a synthetic aperture sonar ping is provided, in which the wavefront comprises 21 million triangles and a rippled seafloor comprises five hundred thousand triangles.