Remote Sensing of Acoustic Signals and Perturbations Generated in Dense Medium

Abstract

Distributed reflections of electromagnetic waves by running acoustic grating in two-layer medium have been considered as the new remote sensing methods for the registration of signals generated in dense medium. The theoretical analysis has been done for the application of this method to atmospheric reception of signal from underwater acoustic source. The effect of unsteady air-water interface irregularities due to wind waves has been examined. Calculations have shown that sufficiently intense acoustic signal can be received from deep ocean (down to kilometer) at a high altitude in atmosphere (up-to kilometers now and higher in future). The completed laboratory experiments have also confirmed the possibility of remote sensing registration of signal from underwater acoustic source. The reception of signal through interface (boundary surface) between different media has application on wide range of scales, from microscale (crystal lattice defect motion, for example) to geophysical one (ocean bottom layers detrusion or underwater volcano eruption, etc). In this situation the signal receiver is disposed in the other medium (usually in air) outside and often away from the dense medium where perturbation (or signal) source under examination is located. In dense conductive medium (such as metal, electrolyte, sea water) the optimal carrier of signal or information about perturbation is the acoustic waves. However acoustic waves attenuate drastically in transiting the interface and relatively soon decay when propagate in air. Therefore immediate registration of such acoustic waves away from the interface is impossible in many cases (particularly in high frequency range).