Figure 7 depicts the 256th frame of the simulation. A standing wave in a plenum diffracts through two slits to show correct interference patterns and Fresnel diffraction from a barrier in front of the slits. Lenses A lens is a material that has a constant sound speed different from that of the surrounding medium. The sound speed profile is modeled fitting a parabola to these two points. The bottom is modeled by tapering the sound speed to zero at the bottom of the screen, so that wavefronts directed downward are not reflected.
Simulation shows that sound beams directed at an angle to the sound axis bend toward the sound axis.
Figure 9 depicts a downward beam bending upward to the left and an upward beam bending downward to the right as it scatters off a school of fish. The sound speed profile is exagerated to show these refractions. The horizontal waves near the top are reflected from the surface. A parabolic sound speed profile refracts sound beams from an obliques shaded source array toward the sound axis of minimu sound speed, with some sound scattered from fish and reflected from the surface. The parabola in Figures 9 and 10 shows the sound speed profile as a function of depth.