FOURIER FORMALISM FOR DESCRIBING NONLINEAR SELF-DEMODULATION OF A PRIMARY NARROW ULTRASONIC BEAM

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. © 1990, Acoustical Society of America. All rights reserved.