Fourier formalism for describing nonlinear self-demodulation of a primary narrow ultrasonic beam

Abstract

Presented here is the derivation of nonlinear interactions that occur within a primary narrow beam for which the temporal spectrum is continuous and narrow. This follows the bases of the Fourier formalism. Acoustics levels are presumed weak enough so that second-order equations may be used. In the quasilinear case, the exact theoretical expression of the created parametric farfield, formed from a transient modulated primary signal, is established, by using weakly restrictive assumptions. The case of high primary levels is discussed. Some experimental results are presented.