Nonlinear acoustics in higher-order approximation: Comment

Some useful expressions for the second- and third-order equations for harmonic generation of infinite plane acoustic waves in a nonlinear non-viscous fluid are corrected. The concern addressed in the present comment is to point out some typographical errors in the first-order velocity and pressure expressions intervening in the calculation of the second-order nonlinear equations, as well as a miscalculation of the axial component of the third-order Lighthill tensor term and the resulting third-order velocity and pressure equations presented in that paper.