Ray method for complete system of acoustic equations with simple caustic correction

Ray theory, applied to optics, obtained its current mathematical form in the work of Sommerfeld and Runge. Epstein’s may be the earliest formulation of the ray theory for ocean acoustics. The mathematical formalism is based on the second order Helmholtz equation asymptotic solution in both cases. Usually, a system of equations is more flexible than any equation derived from it. More critical is that the first-order systems are supported by plenty of numerical methods. The work investigates this option.