NONLINEAR ANALYSIS AND SYNTHESIS OF LAYERED MEDIUM IN ECOLOGICAL MONITORING
We consider the nonlinear analysis and synthesis of layered media. Specified are the commonality and differences of analysis and synthesis in the description of nonlinear processes in acoustics, due to the physical nonlinearity of the layered medium. Obtained in analytical form are general expressions for pressure waves of combination frequencies in nonlinear interaction in a stratified medium. A model is proposed on the basis of which expressions are obtained to estimate the contributions to the field parameters of a parametric acoustic antenna when the interaction medium changes. The model considers ecological systems consisting of various number of discrete layers with constant parameters. The developed model is a discrete additive sum of contributions of all layers that make up the system under consideration. Consideration and analysis is carried out by expressions of transverse and longitudinal aperture factors in each individual layer. The picture of the change in the angular dependence of the amplitude of the longitudinal aperture multiplier of the acoustic parametric antenna when moving the interface in the region of nonlinear interaction of a thin layer of the second (intermediate) medium of constant length on the example of the layered system "Water - Glycerin - Water" is obtained. From this angular dependence, the amplitudes and phases of the longitudinal aperture multiplier of the acoustic parametric antenna for the considered three-layer system are presented when moving the interface in the region of nonlinear interaction. They show significant changes in these characteristics when changing the geometric parameters of the contacting systems. For the three-layer system, the dynamics of the formation of the directivity characteristic with an increase in the length of the third layer is studied. The proposed model of this consideration allows to include the analysis of different layered structures of environmental media by means of nonlinear interaction of acoustic waves. With a known number of layers and their lengths, it becomes possible to determine the ratios of acoustic impedances of contacting media. Numerical results for various layered systems are presented. Similar consideration of the real situation is possible in the case of contact media in the case of blurred layers. Thus, in the analysis and synthesis of layered media in environmental monitoring, it is possible to construct and implement a method for remote determination of parameters of contacting media based on analytical processing of measurement results.