Go back to Chapter 5The simulation software successfully modelled the general behavior of a variety of spherical, liquid-filled acoustic lenses. It was able to predict beam widths and sidelobe heights and positions for various fluid mixes and shell configurations at different temperatures. For thick lenses with thin-walled shells, better results were obtained from using zero-thickness shells with smaller effective than physical apertures. The simulations were also able to predict depth of focus and approximate focal position with this modification.
The primary limitation of the software seems to be the modelling of the propagation of sound through a thin spherical shell. The present model utilizes the solution of the wave equation for a planar interface to calculate transmission coefficients at each side of the shell. This is done by making the assumption that the shell curvature is small compared to the wavelength of sound. The simulation also ignores the components of rays reflected within the lens system, which may reduce its accuracy for some shell configurations.
ALSSP is also able to model thin lenses. Although experimental data on which to test it is still limited, there is no reason to believe that it should not make accurate predictions. As discussed earlier, other researchers have successfully modeled specific thin lenses using similar algorithms. ALSSP extends those algorithms to a more general class of lenses and environment conditions.
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