NONLINEAR ACOUSTICS IN HIGHER-ORDER APPROXIMATION

Based on Lighthill's equation, the n-th order (n > 2) inhomogeneous wa ve equations are established by means of the perturbation method. The third-order nonlinear parameter C/A is defined as a new characteristic parameter in addition to the second-order one B/A. By using the Lagra nge's parameter variation method, the third-order harmonic waves are o btained, in which the accumulation solution have a term proportional t o the square of the distance. It is shown by analysis that all the sol utions are valid only in the region where the accumulation terms are p redominant.