paceFirstOrder3D</a></code>. Compared to ray-tracing or Field II, this approach is very general. In particular, it accounts for nonlinearity, multiple scattering, power law acoustic absorption, and a finite beam width in the elevation direction. However, it is also computationally intensive. Using a modern GPU and the Parallel Computing Toolbox (with <code>'DataCast'</code> set to <code>'gpuArray-single'</code>),  each scan line takes around 3 minutes to compute. Using a modern desktop CPU (with <code>'Data